CN108546114B - Wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and preparation method thereof - Google Patents

Wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and preparation method thereof Download PDF

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CN108546114B
CN108546114B CN201810346749.XA CN201810346749A CN108546114B CN 108546114 B CN108546114 B CN 108546114B CN 201810346749 A CN201810346749 A CN 201810346749A CN 108546114 B CN108546114 B CN 108546114B
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傅邱云
周东祥
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Huazhong University of Science and Technology
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Abstract

The invention discloses a wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and a preparation method thereof, wherein the raw material composition of the negative temperature coefficient thermal sensitive ceramic material comprises BaTiO3、TiO2、M1O、M2O、M3O、M4O and M5O，M1At least 1 element selected from Sm, Nd, Y, La and Nb; m2At least 2 elements of Si, Al and Ti; m3Is a combination of at least 1 element of Sr and Pb and Ca element; m4Sb and at least 1 element of Bi; m5Is at least 1 element of Na, K and Li. According to the invention, the key composition of the ceramic material, the whole process of the corresponding preparation method and the condition parameters of each reaction step are improved and further optimized, and the barium titanate-based wide-temperature-zone NTC thermal sensitive ceramic material with the measurement temperature zone of more than 300 ℃ can be obtained by doping and modifying the barium titanate-based semiconductor thermal sensitive ceramic.

Description

Wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and preparation method thereof
Technical Field
The invention belongs to the technical field of functional ceramic materials, and particularly relates to a wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and a preparation method thereof, in particular to BaTiO3A Negative Temperature Coefficient (NTC) heat-sensitive ceramic material and a preparation method thereof.
Background
Most typical NTC thermal sensitive ceramics are semiconductor ceramic materials based on transition metal oxides such as manganese, cobalt, nickel and the like, and are characterized in that the resistivity of the materials is exponentially reduced along with the rise of the ambient temperature, so that negative resistance temperature (NTC) characteristics are generated. The ceramic material can be used for manufacturing various temperature sensors, has a series of advantages of simple structure, low cost, safety, reliability and the like, is widely applied to the fields of various household appliances, automotive electronics, automatic control, electronic equipment and the like, and has very high practical value and economic value.
The conductivity mechanism of manganese, cobalt, nickel and other transition metal oxides-based semiconductive heat-sensitive ceramic materials is quite complex, generally regarded as polaron conductivity, and in a multielement material system, due to the existence of various ion defects (metal defect, ion valence change and the like), the determinants of the conductivity are complex and variable, but can be generally described by the following mathematical expressions:
Figure BDA0001632139910000011
in the formula: Δ HfActivation energy for ionization defect,. DELTA.HmActivating energy for carrier migration. In general,. DELTA.Hf、ΔHmAll are temperature-related parameters, and can be approximately regarded as constants only in a relatively narrow temperature range allowed by errors, and then the formula (1) can be simplified as follows:
Figure BDA0001632139910000012
because of the more factors related to the B value of NTC semiconductor thermosensitive ceramic materials based on oxides of manganese, cobalt, nickel and other transition metals, it is impossible to prepare a temperature sensor with wide measurement temperature range and high precision requirement, and only the sensors with different material proportions can be prepared in different temperature regions to realize the precise measurement of the wide temperature region. Meanwhile, the semiconductor ceramic material is difficult to prepare the thermosensitive material with low resistivity, high B value, high resistivity and low B value technically, so that the application field and the measurement range of the thermosensitive material are limited.
Transformation of equation (2) yields:
Figure BDA0001632139910000021
the value of B of the material is determined by the formula (3), where R1Is corresponding to a temperature of T1Resistance value at (e.g., 25 ℃), R2Is corresponding to a temperature of T2(e.g., 85 ℃ C.) resistance. T is1、T2Or based on measurement of the elementAnd (4) determining a temperature range.
On the other hand, barium titanate-based semiconductor ceramics are known as a typical Positive Temperature Coefficient (PTC) thermosensitive material, and are characterized in that when the temperature rises to a certain specific temperature (the curie point or switching temperature point), the resistivity thereof increases by several orders of magnitude, a switching-like PTC effect occurs, the resistance before the curie point changes little with the temperature, and the resistance change rate from room temperature to the curie temperature is not more than 1 order of magnitude. The PTC effect of the material is used as a heating element, the heating power of the heating element hardly changes along with the change of the applied voltage, and the heating element has the function of automatic constant temperature. Meanwhile, the PTC characteristic of the material above the Curie temperature can be used for preparing a temperature sensing element, but the temperature measuring region of the temperature sensing element is narrow (generally from room temperature to 100 ℃), the application range is limited, and the temperature sensing element is only applied to a few fields such as automobile water temperature measurement and control.
The invention adopts the defect chemistry and material semiconduction technology to carry out doping modification on the barium titanate ceramic, greatly improves the carrier concentration below the Curie temperature of the material, thereby improving the NTC effect of the material and reducing the PTC effect, and simultaneously realizes the measurement of a wide temperature zone through the movement of the Curie point.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention aims to provide a wide-temperature-zone negative temperature coefficient thermal sensitive ceramic material and a preparation method thereof, wherein the overall process of the corresponding preparation method and condition parameters (such as reaction temperature control) of each reaction step are improved and further optimized by key composition components (including types of specific components, proportions among the specific components and the like) of the ceramic material, and the barium titanate-based semiconductor thermal sensitive ceramic is doped and modified, so that the wide-temperature-zone NTC thermal sensitive ceramic material with a barium titanate base and a measurement temperature zone of more than 300 ℃ can be obtained, and particularly, the preparation of the thermal sensitive material with low resistivity, high B value, high resistivity and low B value can be realized aiming at the defects of manganese, cobalt and nickel transition metal oxide semiconductor thermal sensitive ceramic. The novel barium titanate-based NTC semiconductor thermosensitive ceramic is a wide-temperature-zone NTC thermosensitive ceramic material with a measuring temperature zone of more than 300 ℃, and the material system has the advantages of wide measuring range, good linearity (under a single logarithmic coordinate) and high measuring precision; meanwhile, the average grain size of the material is small (less than 1 micron), the ceramic polycrystal is compact, and the reliability is high.
To achieve the above object, according to one aspect of the present invention, there is provided a negative temperature coefficient thermal sensitive ceramic material characterized in that a raw material composition of the negative temperature coefficient thermal sensitive ceramic material includes BaTiO3、TiO2、M1O、M2O、M3O、M4O and M5O, and BaTiO3、TiO2、M1O、M2O、M3O、M4O and M5The molar ratio of O seven satisfies (1-x-y): (x + y): v: w: x: y: y, wherein v is 0.1-0.5, w is 1.0-5.0, x is 0-40.0, and y is 0.1-10.0; the mutual correspondence of the respective raw materials is shown by the following formula:
(1-x-y)BaTiO3+(x+y)TiO2+vM1O+wM2O+xM3O+y(M4O+M5O)；
further, said M1At least 1 element selected from Sm, Nd, Y, La and Nb;
the M is2At least 2 elements of Si, Al and Ti;
the M is3Is a combination of at least 1 element of Sr and Pb and Ca element;
the M is4Sb and at least 1 element of Bi;
the M is5Is at least 1 element of Na, K and Li.
As a further preferred aspect of the present invention, said M2Wherein the mol ratio of Si, Al or the sum of the two elements (Si + Al) to Ti is 2: 1;
the M is3In the formula, the molar ratio of Sr element, Pb element or the sum of the two elements (Sr + Pb) to Ca element is 3: 1.
according to another aspect of the present invention, there is provided a method for preparing the above negative temperature coefficient thermal sensitive ceramic material, comprising the steps of:
(1) preparing an NTC powder material:
according to BaTiO3、TiO2、M1O、M2O、M3O、M4O、M5BaTiO with target molar ratio of O seven3Source powder, Ti Source powder, M1Source powder, M2Source powder, M3Source powder, M4Source powder and M5Source powder, mixed to obtain mixed powder; then, ball-milling and mixing the mixed powder and a premixed liquid according to the weight ratio of (0.4-0.7) to (0.6-0.3), wherein the premixed liquid is prepared by mixing an organic monomer, a cross-linking agent and water according to the weight ratio of 10: (0.5-1): 100 weight ratio; after ball milling, putting the ball milling slurry into a container, adding a catalyst and an initiator, and standing to solidify the ball milling slurry into a colloid; drying the colloid, removing the colloid, and calcining to obtain an NTC powder material;
(2) preparing NTC heat-sensitive ceramic:
and (2) adding a binder into the NTC powder material obtained in the step (1) for granulation, then molding and sintering at a high temperature of 1250-1350 ℃ to obtain the NTC thermosensitive ceramic.
As a further preferred aspect of the present invention, in the step (2), the sintering is performed at a high temperature of 1250 ℃ to 1350 ℃, specifically, the temperature is first raised to 400 ℃ to 500 ℃ at a heating rate of 150 ℃/h to 200 ℃/h, and the temperature is kept for at least half an hour; then heating to 800-1000 ℃ at the speed of 150-250 ℃/h and preserving heat for at least half an hour, then heating to the sintering temperature of 1250-1350 ℃ at the speed of 300-350 ℃/h for sintering treatment, and cooling at the cooling speed of 200-300 ℃/h after sintering treatment.
In a further preferred embodiment of the present invention, the time for the sintering treatment at the sintering temperature of 1250 to 1350 ℃ is 1 to 3 hours.
In a further preferred embodiment of the present invention, in the step (1), the Ti source powder is TiO2Powder of the M1The source powder is M1Oxide powder of (2), M2The source powder is M2Oxide powder of (2), M3The source powder is M3Oxide powder or carbonate powder of (2), M4The source powder is M4Oxide powder of (2), M5The source powder is M5Oxide powder or carbonate powder of (4); the grain diameters of various source powders mixed to form the mixed powder are all less than 500 nanometers.
In a further preferred embodiment of the present invention, in the step (1), the catalyst and the initiator are added in amounts of 1 to 5ml per 100ml of the ball-milling slurry.
As a further preferred aspect of the present invention, in the step (1), the drying is performed at 100 ℃; the rubber discharging is carried out for 1-3 hours at the temperature of 600 ℃; the calcination is carried out at the temperature of 750-950 ℃ for 1-3 hours.
In a further preferred embodiment of the present invention, in the step (1), the organic monomer is Acrylamide (AM), the crosslinking agent is Methylene Bisacrylamide (MBAM), the catalyst is Tetramethylethylenediamine (TEMD), and the initiator is Ammonium Persulfate (APS) with a mass percentage concentration of 10%.
Compared with the prior art, the barium titanate-based semiconductor thermosensitive ceramic prepared by the technical scheme has the following beneficial effects that the barium titanate-based semiconductor thermosensitive ceramic is subjected to doping modification of specific components and proportions:
1. the novel barium titanate-based NTC thermal sensitive ceramic material has the advantages of wide measuring temperature range, high measuring accuracy, high stability and the like, and simultaneously, the macroscopic electrical properties of the material comprise: the measurement temperature zone, the normal temperature resistance, the material B value and the like are easy to adjust through the material formula. For example, when x is 20 and y is 5, the measurement temperature zone of the material is-60-180 ℃, the normal temperature resistance is 100k omega, and the B value of the material is 2000; when x is 30 and y is 0.5, the measurement temperature zone of the material is-50-250 ℃, the normal-temperature resistance is 500 omega, the B value of the material is 600 and the like.
According to the invention, the barium titanate-based semiconductor thermosensitive ceramic is subjected to doping modification, so that the obtained ceramic material with a specific component composition can be further applied as a negative temperature coefficient thermosensitive ceramic material. In the doped component composition, M1The element Sm, Nd, Y, La, etc. contained in the alloy is doped as a semiconducting elementThe resistivity of the material can be adjusted and controlled so as to meet the temperature measurement requirements of different occasions; m2Si, Al, Ti and other elements contained in the semiconductor ceramic can control the grain size and density of the semiconductor ceramic; m3The Ca, Sr, Pb and other elements contained in the temperature measuring element can adjust the measuring temperature range of the temperature measuring element; m4The B value of the semiconductor ceramic material can be adjusted by the elements such as Sb, Bi and the like contained in the ceramic material; m5The B value of the material of the semiconductor ceramic material can be adjusted by the element contained in (A) or (B). By utilizing the integral comprehensive action of the doping components, the prepared barium titanate-based NTC thermal sensitive ceramic material has the characteristics of wide measurement temperature range, accurate measurement and high stability.
2. In the traditional solid phase method for preparing the thermosensitive ceramic powder, deionized water is generally added as a mixing medium in a material ball-milling mixing process, and if the components contain elements which are easy to dissolve in water, such as Na, K and the like, the loss of the elements which are easy to dissolve in water (such as Na, K) can be caused in the subsequent dehydration process, so that the mismatch of stoichiometric ratio is caused. In order to solve the problems, the invention provides a technology for preparing powder by a solid-phase gel method, solves the problem of loss of water-soluble elements such as Na, K and the like contained in the components, prevents mismatch of stoichiometric ratio, and ensures material performance.
3. By combining with the material formula design, the thermal sensitive ceramic is prepared by adopting a sintering process of rapidly increasing and decreasing the temperature, the temperature is rapidly increased to the sintering temperature, so that the liquid phase additive in the material composition rapidly forms a liquid phase, and the liquid phase additive is wrapped on the surface of crystal grains to form a layer of protective film, thereby effectively preventing elements from volatilizing. The rapid cooling can inhibit the growth of PTC effect and effectively improve NTC effect.
4. The gel calcination temperature is low, the growth and agglomeration of the crystal can be avoided, the high activity is kept, and the volatilization of Pb, Bi and other ions is reduced to a great extent.
5. The NTC thermal sensitive ceramic prepared by the invention has fine grain size which is close to nanometer level, and the ceramic body is compact, thereby ensuring high reliability and long service life of the material.
Drawings
FIG. 1 is a flow chart of the powder preparation of the present invention.
FIG. 2 is a diagram of the sintering process of the present invention.
FIG. 3 is a graph showing resistance-temperature characteristics of samples obtained in examples 1 to 6 of the present invention.
Fig. 4 is a typical microstructure diagram of a sample 6 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The wide-temperature-zone NTC thermal sensitive ceramic material comprises the following raw materials:
(1-x-y)BaTiO3+(x+y)TiO2+vM1O+wM2O+xM3O+y(M4O+M5O)(I)
in the formula (I), v is 0.1-0.5; w is 1.0-5.0; x is 0-40.0; y is 0.1-10.0; all corresponding to the molar ratio content.
In the component (A) M1At least 1 element such as Sm, Nd, Y, La, Nb and the like; m2At least 2 elements of Si, Al, Ti, etc., wherein the molar ratio of Si or Al or the sum of the two elements (Si + Al) to Ti is 2: 1, i.e., the molar ratio of Si to Ti is 2: 1, or the molar ratio of Al to Ti is 2: 1, or the molar ratio of (Si + Al) to Ti is 2: 1; m3Ca, Sr, Pb, etc., at least Ca in combination with 1 element of Sr, Pb, wherein the molar ratio of Ca to Pb or Sr, or Ca to (Pb + Sr) is 1: 3, i.e., the molar ratio of Ca: pb 1: 3, or the molar ratio of Ca: sr is 1: 3, or the molar ratio of Ca to (Pb + Sr) is 1: 3; m4At least 1 element such as Sb, Bi and the like; m5At least 1 element such as Na, K, Li, etc. The initial raw materials are related metal oxides such as Y with purity of 99.8% or more2O3、Sm2O3、TiO2、Bi2O3Etc.; or carbonates, e.g. CaCO3、SrCO3And the like; barium titanate powderBaTiO with the purity of more than 99.8 percent is adopted3And (3) powder. Meanwhile, the grain diameter of various raw material powder is required to be less than 800 nanometers.
M1The elements of Sm, Nd, Y, La and the like contained in the alloy are doped as semiconductors, and the aim is to adjust and control the resistivity of the material so as to meet the temperature measurement requirements of different occasions;
M2the elements contained in the ceramic material, such as Si, Al, Ti and the like, are used for controlling the grain size and the density of the semiconductor ceramic;
M3the Ca, Sr, Pb and other elements contained in the temperature measuring element are used for adjusting the measuring temperature range of the temperature measuring element;
M4the elements such as Sb, Bi and the like contained in the material are used for adjusting the B value of the semiconductor ceramic material;
M5the element contained in (A) is a material B value for adjusting the semiconductor ceramic material.
The negative temperature coefficient thermal sensitive ceramic material is an NTC thermal sensitive ceramic (element) which is prepared by calcining raw materials in the composition proportion of a formula (I) to form a single perovskite structure, and particularly sintering at the high temperature of 1250-1350 ℃.
The invention relates to a semiconductor NTC heat-sensitive ceramic material and a preparation method thereof, and also relates to special preparation technologies such as a specific material ratio, a solid-phase gel method for preparing nano powder, a rapid temperature rise and drop firing process and the like. The specific introduction is as follows:
1. preparation of nano powder by solid phase gel method
The ingredients are prepared according to the proportion of a formula (I):
(1-x-y)BaTiO3+(x+y)TiO2+vM1O+wM2O+xM3O+y(M4O+M5O)(I)
wherein: v is 0.1 to 0.5; w is 1.0-5.0; x is 0-40.0; y is 0.1-10.0; all correspond to the percentage content;
because the components contain Na, K and other water-soluble components, if the components are synthesized by adopting a traditional solid phase method, the water is sent out by a filter pressing method, so that the loss of the water-soluble Na, K and other element components is avoided, and the mismatch of the stoichiometric ratio is caused. But do notIf a liquid phase sol-gel process is used (e.g., CN101830698B), the water-insoluble material (e.g., SiO) must first be removed2) The preparation of the citrate soluble in water can greatly improve the manufacturing cost, so the invention provides a technology for preparing powder by adopting a solid-phase gel method, and the specific flow is shown in figure 1.
The method specifically comprises the following steps:
firstly, preparing a premixed solution, and preparing the premixed solution according to the mass ratio of the organic monomer, the cross-linking agent and the water of 10 to (0.5-1) to 100, as shown in figure 1. After the preparation of the premixed liquid is finished, ball-milling and mixing the mixed powder and the premixed liquid which are weighed according to the formula (I), wherein the powder and the premixed liquid are (0.4-0.7) to (0.6-0.3), the mass ratio is the mass ratio, and the ball-milling time is 1-3 hours;
secondly, after the ball milling is finished, the ball milling slurry is placed into a container, the catalyst is added while stirring, after the catalyst is added, the slurry is continuously stirred, and the initiator solution is dropwise added, wherein about 1-5 ml of the catalyst and about 5ml of the initiator are respectively needed for every 100ml of the slurry. Standing after dripping, and solidifying the slurry into a colloid;
thirdly, the solidified colloid is put into an oven to be dried at the temperature of 100 ℃;
and fourthly, calcining, namely discharging the colloid at 600 ℃ for 1-3 hours, then calcining at 750-950 ℃, and preserving heat for 1-3 hours to obtain the NTC powder material.
The organic monomer in the premix may be Acrylamide (AM) and the crosslinking agent may be methylenebisacrylamide (MBAM).
The catalyst can be tetramethyl ethylene diamine (TEMD), the initiator can be ammonium sulfate (APS) with over concentration of 10%, and the preparation method comprises the steps of weighing and mixing APS and H according to the mass ratio2O＝1∶9。
2. Preparation of NTC thermosensitive ceramic
And adding the obtained powder into an adhesive for granulation, dry pressing for molding, and sintering at the high temperature of 1250-1350 ℃ for 1-3 hours to obtain the NTC thermal sensitive ceramic resistor.
As the material composition contains a large amount of volatile elements such as Na, K, Bi, Sb, Pb and the like, a special sintering process is required, and the invention provides the sintering process shown in figure 2.
Specifically, the temperature is raised to 400-500 ℃ at the heating rate of 150-200 ℃/h and is kept for at least half an hour, so as to remove organic matters (such as adhesive added in molding) in the blank; then heating to 800-1000 ℃ at the speed of 150-250 ℃/h and preserving heat for at least half an hour, then heating to the sintering temperature of 1250-1350 ℃ at the speed of 300-350 ℃/h for sintering treatment, and rapidly heating from (800-1000 ℃) to the sintering temperature (1250-1350 ℃) to prevent the volatile elements from volatilizing, wherein the principle is as follows: the rapid heating to the sintering temperature can enable the liquid phase additive in the material composition to rapidly form a liquid phase, and the liquid phase additive is wrapped on the surface of the crystal grain to form a layer of protective film, so that the element volatilization can be effectively prevented. The purpose of keeping the temperature for half an hour in the temperature range of (800 ℃ -1000 ℃) is to enable the sintering furnace to be heated up more effectively and rapidly, which is equivalent to rest midway for applying force. After the sintering treatment is finished, cooling to room temperature at a cooling rate of 200-300 ℃/h, wherein the rapid cooling is used for inhibiting the generation of PTC effect and effectively improving NTC effect.
In the following 1 to 6 examples of the present invention, the raw material used is barium titanate (BaTiO)3) Calcium carbonate (CaCO)3) Sodium carbonate (Na)2CO3) Titanium dioxide (TiO)2) Yttrium oxide (Y)2O3) Silicon dioxide (SiO)2) Bismuth oxide (Bi)2O3) And the purity is more than 99.8%; the organic monomer is Acrylamide (AM), and the cross-linking agent is Methylene Bisacrylamide (MBAM); the catalyst was Tetramethylethylenediamine (TEMD) and the initiator was Ammonium Persulfate (APS) at a concentration of 10%.
The sample ratios and associated electrical properties are shown in table 1 and fig. 3.
Table 1 table of the material formulations of the examples
Figure BDA0001632139910000101
In the embodiments 1-6, the sintering processes shown in Table 2 and FIG. 2 are respectively adopted, the sintering results of the material B value are also shown in Table 2, and the resistance temperature characteristic curve is shown in FIG. 3. FIG. 4 is a microstructure diagram of the ceramic material of example 6.
Table 2: sintering process and material B value sintering result table of each embodiment
Figure BDA0001632139910000102
In addition to the organic monomers used in the above examples, other organic monomers for sol-gel, and corresponding catalysts, initiators, etc. may be used in the present invention.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. The negative temperature coefficient thermal sensitive ceramic material is characterized in that the raw material composition of the negative temperature coefficient thermal sensitive ceramic comprises BaTiO3、TiO2、M1O、M2O、M3O、M4O and M5O, and BaTiO3、TiO2、M1O、M2O、M3O、M4O and M5The molar ratio of O seven satisfies (1-x-y): (x + y): v: w: x: y: y, wherein v = 0.1-0.5, w = 1.0-5.0, x = 0-40.0, and y = 0.1-10.0, all corresponding to the percentage content; the mutual correspondence of the respective raw materials is shown by the following formula:
(1-x-y)BaTiO3+(x+y)TiO2+vM1O+wM2O+xM3O+y(M4O+M5O)；
further, said M1At least 1 element selected from Sm, Nd, Y, La and Nb;
the M is2At least 2 elements of Si, Al and Ti;
the M is3Is a combination of at least 1 element of Sr and Pb and Ca element;
the M is4Is Sb, and Bi1 element is reduced;
the M is5Is at least 1 element of Na, K and Li.
2. The ntc material of claim 1, wherein M is2Is the combination of at least 1 element of Si and Al and Ti, and the molar ratio of Si, Al or the sum of the two elements (Si + Al) to Ti is 2: 1;
the M is3In the formula, the molar ratio of Sr element, Pb element or the sum of the two elements (Sr + Pb) to Ca element is 3: 1.
3. a method of preparing a negative temperature coefficient thermal sensitive ceramic material according to claim 1 or 2, comprising the steps of:
(1) preparing an NTC powder material:
according to BaTiO3、TiO2、M1O、M2O、M3O、M4O、M5BaTiO with target molar ratio of O seven3Source powder, Ti Source powder, M1Source powder, M2Source powder, M3Source powder, M4Source powder and M5Source powder, mixed to obtain mixed powder; then, mixing the mixed powder and the premixed solution according to the weight ratio of (0.4-0.7): (0.6-0.3), and performing ball milling mixing, wherein the premixed solution is prepared by mixing an organic monomer, a crosslinking agent and water according to the weight ratio of 10: (0.5-1): 100 weight ratio; after ball milling, putting the ball milling slurry into a container, adding a catalyst and an initiator, and standing to solidify the ball milling slurry into a colloid; drying the colloid, removing the colloid, and calcining to obtain an NTC powder material;
(2) preparing NTC heat-sensitive ceramic:
and (2) adding a binder into the NTC powder material obtained in the step (1) for granulation, then molding and sintering at a high temperature of 1250-1350 ℃ to obtain the NTC thermosensitive ceramic.
4. The preparation method according to claim 3, wherein in the step (2), the sintering is carried out at a high temperature of 1250-1350 ℃, specifically, the temperature is raised to 400-500 ℃ at a temperature raising rate of 150-200 ℃/h and is kept for at least half an hour; then heating to 800-1000 ℃ at the rate of 150-250 ℃/h, preserving heat for at least half an hour, then heating to the sintering temperature of 1250-1350 ℃ at the rate of 300-350 ℃/h, sintering, and cooling at the cooling rate of 200-300 ℃/h after sintering.
5. The method according to claim 3, wherein the sintering treatment is carried out at a sintering temperature of 1250 ℃ to 1350 ℃ for 1 to 3 hours.
6. The method according to claim 3, wherein in the step (1), the Ti source powder is TiO2Powder of the M1The source powder is M1Oxide powder of (2), M2The source powder is M2Oxide powder of (2), M3The source powder is M3Oxide powder or carbonate powder of (2), M4The source powder is M4Oxide powder of (2), M5The source powder is M5Oxide powder or carbonate powder of (4); the grain diameters of various source powders mixed to form the mixed powder are all less than 500 nanometers.
7. The preparation method according to claim 3, wherein in the step (1), the catalyst and the initiator are added in amounts respectively satisfying 1-5 ml per 100ml of the ball-milling slurry.
8. The method according to claim 3, wherein in the step (1), the drying is carried out at 100 ℃; the rubber discharging is carried out for 1-3 hours at the temperature of 600 ℃; the calcination is carried out at the temperature of 750-950 ℃ for 1-3 hours.
9. The method according to claim 3, wherein in the step (1), the organic monomer is Acrylamide (AM), the crosslinking agent is methylenebisacrylamide (MBAM), the catalyst is Tetramethylethylenediamine (TEMD), and the initiator is Ammonium Persulfate (APS) at a concentration of 10% by mass.
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