CN117142856A - Nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target material - Google Patents
Nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target material Download PDFInfo
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- CN117142856A CN117142856A CN202311168314.8A CN202311168314A CN117142856A CN 117142856 A CN117142856 A CN 117142856A CN 202311168314 A CN202311168314 A CN 202311168314A CN 117142856 A CN117142856 A CN 117142856A
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- 239000000919 ceramic Substances 0.000 title claims abstract description 77
- HEOGEEMADXKTBU-UHFFFAOYSA-N [O].[Mn].[Ca].[La] Chemical compound [O].[Mn].[Ca].[La] HEOGEEMADXKTBU-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 239000013077 target material Substances 0.000 title abstract description 35
- 239000011575 calcium Substances 0.000 claims abstract description 68
- 239000011572 manganese Substances 0.000 claims abstract description 61
- 239000000126 substance Substances 0.000 claims abstract description 5
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 93
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 93
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 91
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 70
- 239000011259 mixed solution Substances 0.000 claims description 55
- 239000000843 powder Substances 0.000 claims description 49
- 238000010438 heat treatment Methods 0.000 claims description 45
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 42
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 claims description 40
- 238000003756 stirring Methods 0.000 claims description 40
- 239000000499 gel Substances 0.000 claims description 34
- 239000002904 solvent Substances 0.000 claims description 29
- 238000001816 cooling Methods 0.000 claims description 28
- 238000000227 grinding Methods 0.000 claims description 22
- 239000011240 wet gel Substances 0.000 claims description 22
- 238000002156 mixing Methods 0.000 claims description 21
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 claims description 21
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 20
- 239000002243 precursor Substances 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 14
- 238000002360 preparation method Methods 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 11
- KFNJUIWVLBMCPW-UHFFFAOYSA-N calcium lanthanum(3+) manganese(2+) oxygen(2-) Chemical compound [O-2].[Mn+2].[La+3].[Ca+2] KFNJUIWVLBMCPW-UHFFFAOYSA-N 0.000 claims description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 2
- 238000003825 pressing Methods 0.000 claims description 2
- 238000005245 sintering Methods 0.000 claims description 2
- 238000010304 firing Methods 0.000 claims 1
- 239000012212 insulator Substances 0.000 abstract description 38
- 229910052751 metal Inorganic materials 0.000 abstract description 26
- 239000002184 metal Substances 0.000 abstract description 26
- 230000007704 transition Effects 0.000 abstract description 24
- 239000000463 material Substances 0.000 abstract description 10
- 230000005290 antiferromagnetic effect Effects 0.000 abstract 1
- 230000005294 ferromagnetic effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 23
- 230000005291 magnetic effect Effects 0.000 description 20
- 238000000034 method Methods 0.000 description 18
- 230000009466 transformation Effects 0.000 description 16
- 239000002738 chelating agent Substances 0.000 description 9
- 239000000084 colloidal system Substances 0.000 description 9
- 239000002270 dispersing agent Substances 0.000 description 9
- 238000001704 evaporation Methods 0.000 description 9
- 239000011858 nanopowder Substances 0.000 description 9
- 238000000465 moulding Methods 0.000 description 8
- 230000007423 decrease Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000003980 solgel method Methods 0.000 description 3
- 238000010532 solid phase synthesis reaction Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012776 electronic material Substances 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000724 energy-dispersive X-ray spectrum Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000005298 paramagnetic effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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Abstract
The invention discloses a nickel-doped lanthanum-calcium-manganese-oxygen polycrystalline ceramic target, and belongs to the technical field of electronic ceramics. The chemical formula of the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target material prepared by sol-gel is La 0.67 Ca 0.33 Mn 1‑x Ni x O 3 Wherein 0 < x < 0.05. The Ni is doped with La 0.67 Ca 0.33 Mn 1‑x Ni x O 3 On one hand, the Mn position of the polycrystalline ceramic target material increases the resistivity by utilizing the influence of Mn position doping on the material resistance, so that the transition temperature of the metal insulator shifts to a low-temperature region. On the other hand, increasing the doping amount of Ni can increase the disorder of the system, and the ferromagnetic clusters are separated, so that the antiferromagnetic property of the system is increased.
Description
Technical Field
The invention belongs to the technical field of electronic ceramics, and particularly relates to a nickel-doped lanthanum-calcium-manganese-oxygen polycrystalline ceramic target.
Background
With the development of technology, strongly-associated electronic materials play an increasingly important role in new functional materials. Perovskite manganese oxide is an important branch in strongly associated electronic materials, and has unique physical properties such as metal insulator transition, giant magnetoresistance effect and the like. Wherein the metal-insulator transition refers to a material having a metal-insulator transition temperature (T MI ) At T MI The material is in a metallic state, and the resistivity is increased along with the temperature; at T MI The material assumes an insulating state as above, and the resistivity decreases with increasing temperature. The giant magnetoresistance effect refers to the resistance of the material, which is obviously reduced under the action of an external magnetic field. Reluctance (MR), which represents the degree of sensitivity of the material resistance to magnetic fields, is an important parameter in the manufacture of magnetic sensors.Wherein ρ is 0 Representing the resistivity at 0T magnetic field ρ H Representing the resistivity at 1T magnetic field.
Transport Properties of Transitional Metal(Ni 2+ )Doped La 0.67 Ca 0.33 MnO 3 Rare-Earth Manganites discloses the preparation of La using the solid phase method 0.67 Ca 0.33 Mn 1-x Ni x O 3 Materials, but materials prepared by solid phase methods have low Magnetic Resistance (MR).
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the chemical formula of the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target is La 0.67 Ca 0.33 Mn 1-x Ni x O 3 Wherein x is more than 0 and less than 0.05;
the preparation method of the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target comprises the following steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent according to the chemical formula of the nickel-doped lanthanum calcium manganese oxide polycrystalline ceramic target, uniformly mixing to obtain a system A, and stirring the system A until the solid is completely dissolved to obtain a mixed solution B;
(2) Adding glycol into the mixed solution B to obtain a mixed solution C;
(3) Placing the mixed solution C at the temperature of 80-90 ℃ and stirring at a constant temperature until the mixed solution C is converted into wet gel D;
(4) Drying and grinding the wet gel D to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E;
(5) Grinding and pressing the nanoscale precursor powder E to form, and performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 1-x Ni x O 3 Polycrystalline ceramic targets.
As a preferred embodiment of the present invention, the molar ratio of nickel nitrate to citric acid is x:4-5, wherein 0 < x < 0.05.
As a preferred embodiment of the present invention, the molar ratio of methanol to lanthanum nitrate is 154-155:1.
as a preferred embodiment of the present invention, the molar ratio of ethylene glycol to lanthanum nitrate is 6 to 7:1.
as a preferred embodiment of the present invention, in the step (4), the drying temperature is 140 to 180℃and the time is 8 to 12 hours.
In the step (4), as a preferred embodiment of the present invention, the burn-in treatment is specifically: the gel powder is heated to 200 ℃ at a constant speed within 1.5-2 h, then heated to 400 ℃ at a constant speed within 1.5-2 h, kept for 0.5h, finally heated to 500 ℃ within 0.5-1 h, kept for 8h, and then naturally cooled to room temperature.
As a preferred embodiment of the present invention, in the step (5), the secondary roasting specifically includes: heating to 600 ℃ at a constant speed within 200min, heating to 1450 ℃ at a constant speed within 213min, preserving heat for 12h, and cooling to 700 ℃ at a constant speed within 188 min.
The principle of the Ni-doped lanthanum calcium manganese oxygen polycrystalline ceramic target material is as follows:
la according to the present invention 0.67 Ca 0.33 Mn 1-x Ni x O 3 In the polycrystalline ceramic target, ni is doped at Mn, and the Mn doping can enable new magnetic exchange interaction between adjacent Mn ions to be generated, and the magnetic order can be changed more directly, so that the resistivity of the material is increased, the trend of resistivity reduction when the temperature is reduced is restrained, and the transition temperature of the metal insulator shifts to a low-temperature region. When an external magnetic field is applied to the target, the spin direction of electrons is influenced by the magnetic field, and the spin arrangement is more ordered, thereby being beneficial to e g The electron transitions and thus the resistivity decreases. Spin disorder still occurs in the high temperature region, which assumes a paramagnetic insulating state, and the application of a magnetic field apparently delays this transition, after which the metal-insulator transition temperature increases. Under the action of a magnetic field, the system becomes ordered, which is favorable for transporting electrons, and the reduction amplitude of the resistivity can influence the MR value. On the one hand, as the Ni doping amount increases, the resistivity of the target increases, and the MR increases as the decrease after the magnetic field is applied increases. On the other hand, the further increase of Ni increases the degree of lattice distortion of the system, the magnetic disorder of the system becomes larger, the response degree of the sample to a magnetic field is reduced, and the MR is reduced.
Compared with the prior art, the invention has the beneficial effects that: the invention adopts a sol-gel method to dope Ni into La 0.67 Ca 0.33 Mn 1-x Ni x O 3 On one hand, the Mn position of the polycrystalline ceramic target material increases the resistivity by utilizing the influence of Mn position doping on the material resistance, so that the transition temperature of the metal insulator shifts to a low-temperature region. On the other hand, increasing the doping amount of Ni can increase the disorder of the system, the resistivity of the target material can be increased, the resistivity is reduced more after the magnetic field is applied, and the MR value is increased.
Drawings
FIG. 1 shows La prepared in examples 1-4 and comparative examples 1-2 of the present invention 0.67 Ca 0.33 Mn 1-x Ni x O 3 ρ -T plot for a polycrystalline ceramic target at 0T.
FIG. 2 shows La prepared in examples 1-4 and comparative examples 1-2 of the present invention 0.67 Ca 0.33 Mn 1-x Ni x O 3 ρ -T plot for a polycrystalline ceramic target at 1T.
FIG. 3 shows La prepared in example 1 of the present invention 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 XRD pattern of polycrystalline ceramic target.
FIG. 4 shows La prepared in example 1 of the present invention 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 SEM profile of polycrystalline ceramic target.
FIG. 5 shows La prepared in example 1 of the present invention 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 EDS spectrum of polycrystalline ceramic target.
FIG. 6 shows La prepared in examples 1-4 and comparative examples 1-2 of the present invention 0.67 Ca 0.33 Mn 1-x Ni x O 3 MR curve contrast plot for polycrystalline ceramic targets.
In the figure, 0 is La prepared in comparative example 1 0.67 Ca 0.33 MnO 3 0.01 is La prepared in example 2 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 0.02 is La prepared in example 3 0.67 Ca 0.33 Mn 0.98 Ni 0.02 O 3 0.03 is La prepared in example 1 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 0.04 is La prepared in example 4 0.67 Ca 0.33 Mn 0.96 Ni 0.04 O 3 0.05 is La prepared in comparative example 2 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 。
Detailed Description
For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples.
Example 1
La (La) 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into 50mL of methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.97:0.03:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding 3mL of ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 Polycrystalline ceramic targets.
As can be seen from FIG. 3, la 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The polycrystalline ceramic target material has a single-phase structure and is not detectedA second phase; and has no impurity peak and good crystallization quality.
As can be seen from FIG. 4, la 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The crystal grains of the polycrystalline ceramic target material are uniformly distributed, the density is high, and the crystallization quality is high.
As can be seen from FIG. 5, la 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The element distribution ratio of the polycrystalline ceramic target is consistent with theoretical calculation, which shows that the prepared sample has good uniformity.
As can be seen from FIGS. 1, 2 and 6, la of this embodiment 0.67 Ca 0.33 Mn 0.97 Ni 0.03 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0536 omega cm, and the transformation temperature of the metal insulator is 239.2K; the resistivity (ρ) of the metal-insulator transition point at 1T was 0.0417 Ω·cm, the metal-insulator transition temperature was 251.5K, and the peak magnetoresistance temperature coefficient (MR) was 67.9%.
Example 2
La (La) 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into 50mL of methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.99:0.01:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding 3mL of ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 Polycrystalline ceramic targets.
As can be seen from FIGS. 1-2 and 6, la of this example 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0247 omega cm, and the transformation temperature of the metal insulator is 258.5K; the resistivity (ρ) of the metal-insulator transition point at 1T was 0.0260 Ω·cm, the metal-insulator transition temperature was 270.6K, and the peak magnetoresistance temperature coefficient (MR) was 64.4%.
Example 3
La (La) 0.67 Ca 0.33 Mn 0.98 Ni 0.02 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.98:0.02:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.98 Ni 0.02 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.98 Ni 0.02 O 3 Polycrystalline ceramic targets.
As can be seen from FIGS. 1-2 and 6, la of this example 0.67 Ca 0.33 Mn 0.98 Ni 0.02 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0373 Ω & cm, and the transformation temperature of the metal insulator is 249.2K; the resistivity (ρ) of the metal-insulator transition point at 1T was 0.0300Ω·cm, the metal-insulator transition temperature was 261.2K, and the peak magnetoresistance temperature coefficient (MR) was 66.4%.
Example 4
La (La) 0.67 Ca 0.33 Mn 0.96 Ni 0.04 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.96:0.04:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 155:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.96 Ni 0.04 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.96 Ni 0.04 O 3 Polycrystalline ceramic targets.
As can be seen from FIGS. 1-2 and 6, la of this example 0.67 Ca 0.33 Mn 0.96 Ni 0.04 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0663 ohm cm, and the transformation temperature of the metal insulator is 228.3K; the resistivity (ρ) at the transition point of the metal insulator at 1T is 0.0485 Ω cm, the metal insulator transitionThe temperature change was 242.9K, and the peak magnetoresistance temperature coefficient (MR) was 65.3%.
Comparative example 1
La (La) 0.67 Ca 0.33 MnO 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent, and uniformly mixing to obtain a system A; wherein the molar ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:1:4.67, methanol is used as a colloid chelating solvent, and the molar ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 MnO 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 MnO 3 Polycrystalline ceramic targets.
As can be seen from FIGS. 1-2 and 6, this comparisonExample La 0.67 Ca 0.33 MnO 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0247 omega cm, and the transformation temperature of the metal insulator is 266.6K; the resistivity (ρ) of the MIT at 1T was 0.0212Ω cm, the MIT transition temperature was 278.4K, and the peak magnetoresistance temperature coefficient (MR) was 60.3%.
Comparative example 1 significantly reduced peak magnetoresistance temperature coefficient (MR) compared to the example because of La 0.67 Ca 0.33 MnO 3 After the polycrystalline ceramic target is doped with Ni, the system becomes ordered under the action of a magnetic field, so that the transportation of electrons is facilitated, and the MR value can be influenced by the resistivity reduction amplitude. On the one hand, as the Ni doping amount increases, the resistivity of the target increases, and the MR increases as the decrease after the magnetic field is applied increases.
Comparative example 2
La (La) 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.95:0.05:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 Polycrystalline ceramic targets.
As can be seen from FIGS. 1-2 and 6, la of this comparative example 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 The resistivity (ρ) of the metal-insulator transition point of the polycrystalline ceramic target at 0T was 0.0902 Ω·cm, the resistivity (ρ) of the metal-insulator transition point at 1T was 0.0645 Ω·cm, and the peak magnetoresistance temperature coefficient (MR) was 60.9%.
Comparative example 2 compared with the example, the peak magnetoresistance temperature coefficient (MR) was significantly reduced because of La 0.67 Ca 0.33 Mn 0.95 Ni 0.05 O 3 The polycrystalline ceramic target is doped with more Ni, so that the degree of lattice distortion of the system is increased, the magnetic disorder of the system is increased, the response degree of a sample to a magnetic field is reduced, and the MR is reduced.
Comparative example 3
La (La) 0.67 Ca 0.33 MnO 3 ：Ni 0.01 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate and citric acid into 50mL of methanol solvent, and uniformly mixing to obtain a system A; wherein the molar ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:1:4.67, methanol is used as a colloid chelating solvent, and the molar ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding 3mL of ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing the nano powder E obtained in the step (4) with nickel powder according to La 0.67 Ca 0.33 MnO 3 ：Ni 0.01 Mixing, grinding and forming the Ni content in the polycrystalline ceramic target material, and then performing secondary roasting to obtain La 0.67 Ca 0.33 MnO 3 ：Ni 0.01 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 MnO 3 ：Ni 0.01 Polycrystalline ceramic targets.
La of this comparative example 0.67 Ca 0.33 MnO 3 ：Ni 0.01 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0519 Ω & cm, and the transformation temperature of the metal insulator is 237.2K; the resistivity (. Rho.) at the transition point of the metal insulator at 1T was 0.0326. Omega. Multidot.cm, and the peak magnetoresistance temperature coefficient (MR) was 57.2%.
Comparative example 3 significantly reduced peak magnetoresistance temperature coefficient (MR) compared to the example because La was prepared using sol-gel method 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The polycrystalline ceramic target has better uniformity, and the comparative example is that La is prepared by a sol-gel method 0.67 Ca 0.33 MnO 3 Precursor powder is mixed with nickel by a solid phase method to prepare La 0.67 Ca 0.33 MnO 3 ：Ni 0.01 The polycrystalline ceramic target is less uniform, and therefore the MR value is significantly reduced.
Comparative example 4
La (La) 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into 50mL of methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.99:0.01:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding 3mL of ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises the steps of uniformly heating gel powder to 200 ℃ within 100min, uniformly heating to 400 ℃ within 100min, preserving heat for 0.5h, heating to 500 ℃ within 0.5h, preserving heat for 8h, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E in the step (4), performing secondary roasting for 12 hours at 1450 ℃, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 Polycrystalline ceramic targets.
La of this comparative example 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0431 omega cm, and the transformation temperature of the metal insulator is 258.3K; the resistivity (. Rho.) at the transition point of the metal insulator at 1T was 0.0348. Omega. Cm, the transition temperature of the metal insulator was 269.2K, and the peak magnetoresistance temperature coefficient (MR) was 56.1%.
Comparative example 4 compared with the example, the peak magnetoresistance temperature coefficient (MR) was significantly reduced because of La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The preparation method of the polycrystalline ceramic target adopts different secondary roasting modes: the example is to raise the temperature to 1450 ℃ in a sectional way, but the comparative example is to raise the temperature to 1450 ℃ at a constant speed, so that the roasting mode of the comparative example 4 affects the growth of crystal grains, the speed is slow in the early stage of roasting, the abnormal growth of the crystal grains is easy to be caused by the constant temperature raising in the whole process, and the performance of the target material is reduced.
Comparative example 5
La (La) 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The preparation method of the polycrystalline ceramic target comprises the following specific steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into 50mL of methanol solvent, and uniformly mixing to obtain a system A; wherein the mole ratio of lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid is 0.67:0.33:0.99:0.01:4.67, methanol is used as a colloid chelating solvent, and the mole ratio of methanol to lanthanum nitrate is 154:1.
(2) Stirring the system A until the solid is completely dissolved to obtain a mixed solution B, and dropwise adding 3mL of ethylene glycol into the mixed solution B to obtain a mixed solution C; wherein ethylene glycol is used as a dispersing agent, citric acid is used as a chelating agent, and the molar ratio of the ethylene glycol to lanthanum nitrate is 6:1.
(3) Placing the mixed solution C obtained in the step (2) at 88 ℃ for stirring and constant temperature treatment, and slowly evaporating the solvent until the mixed solution C is converted into wet gel D; wherein the stirring rate gradually slows down when the sol becomes viscous during stirring.
(4) Drying the wet gel D in the step (3) for 12 hours at the temperature of 140 ℃, grinding to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E; the presintering method comprises uniformly heating gel powder to 500 deg.C for 8 hr within 260min, and naturally cooling to room temperature.
(5) Mixing, grinding and molding the nano powder E obtained in the step (4), and then performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The method of the secondary roasting of the polycrystalline ceramic target material comprises the steps of uniformly heating the pressed target material to 600 ℃ in 200min, uniformly heating to 1450 ℃ in 213min, preserving heat for 12h, uniformly cooling to 700 ℃ in 188min, and naturally cooling to room temperature to obtain La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 Polycrystalline ceramic targets.
La of this comparative example 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 The resistivity (rho) of the transformation point of the metal insulator of the polycrystalline ceramic target material at 0T is 0.0462 omega cm, and the transformation temperature of the metal insulator is 258.3K; the resistivity (ρ) of the metal-insulator transition point at 1T was 0.0339 Ω·cm, the metal-insulator transition temperature was 270.2K, and the peak magnetoresistance temperature coefficient (MR) was 50.3%.
Comparative example 5 compared with the example, the peak magnetoresistance temperature coefficient (MR) was significantly reduced because of La 0.67 Ca 0.33 Mn 0.99 Ni 0.01 O 3 Different presintering modes are adopted in the preparation method of the polycrystalline ceramic target, and in the embodiment, the temperature is uniformly raised to 400 ℃ and then is kept for 0.5h, so that organic matters in the gel powder are fully volatilized; in comparative example 5, the multi-stage pre-sintering mode is not adopted, the heat preservation time is not set, and partial organic matters remain in the finally obtained precursor powder, so that the target performance is reduced.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.
Claims (7)
1. A nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target is characterized in that the chemical formula is La 0.67 Ca 0.33 Mn 1-x Ni x O 3 Wherein x is more than 0 and less than 0.05;
the preparation method of the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target comprises the following steps:
(1) Adding lanthanum nitrate, calcium nitrate, manganese nitrate, nickel nitrate and citric acid into a methanol solvent according to the chemical formula of the nickel-doped lanthanum calcium manganese oxide polycrystalline ceramic target, uniformly mixing to obtain a system A, and stirring the system A until the solid is completely dissolved to obtain a mixed solution B;
(2) Adding glycol into the mixed solution B to obtain a mixed solution C;
(3) Placing the mixed solution C at the temperature of 80-90 ℃ and stirring at a constant temperature until the mixed solution C is converted into wet gel D;
(4) Drying and grinding the wet gel D to obtain gel powder, and presintering the gel powder to obtain nanoscale precursor powder E;
(5) Grinding and pressing the nanoscale precursor powder E to form, and performing secondary roasting to obtain La 0.67 Ca 0.33 Mn 1- x Ni x O 3 Polycrystalline ceramic targets.
2. The nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target of claim 1, wherein the molar ratio of nickel nitrate to citric acid is x:4-5, wherein 0 < x < 0.05.
3. The nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target according to claim 1, wherein the molar ratio of methanol to lanthanum nitrate is 154-155:1.
4. the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target according to claim 1, wherein the molar ratio of ethylene glycol to lanthanum nitrate is 6-7:1.
5. the nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target according to claim 1, wherein in the step (4), the drying temperature is 140-180 ℃ and the drying time is 8-12 hours.
6. The nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target according to claim 1, wherein in the step (4), the pre-sintering treatment specifically comprises: the gel powder is heated to 200 ℃ at a constant speed within 1.5-2 h, then heated to 400 ℃ at a constant speed within 1.5-2 h, kept for 0.5h, finally heated to 500 ℃ within 0.5-1 h, kept for 8h, and then naturally cooled to room temperature.
7. The nickel-doped lanthanum calcium manganese oxygen polycrystalline ceramic target according to claim 1, wherein in the step (5), the secondary firing specifically comprises: heating to 600 ℃ at a constant speed within 200min, heating to 1450 ℃ at a constant speed within 213min, preserving heat for 12h, and cooling to 700 ℃ at a constant speed within 188 min.
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