CN111056836A - Preparation method of high-Tc low-resistance lead-free PTC material - Google Patents

Preparation method of high-Tc low-resistance lead-free PTC material Download PDF

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CN111056836A
CN111056836A CN201911392670.1A CN201911392670A CN111056836A CN 111056836 A CN111056836 A CN 111056836A CN 201911392670 A CN201911392670 A CN 201911392670A CN 111056836 A CN111056836 A CN 111056836A
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朱兴文
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Jiangsu Jun Porcelain Technology Co ltd
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Abstract

The invention relates to a preparation method of lead-free positive temperature coefficient thermistor ceramic with high Curie temperature, high lift-drag ratio and low room temperature resistivity, which is sintered under atmospheric atmosphere, and the method adopts the following formula: x (Bi)1/2Na1/2)TiO3‑yCaTiO3‑(1‑x‑y)BaTiO3+aLi2CO3+bSb2O3A powder wherein x is 0.01 to 0.12, y is 0 to 0.20, a is 0 to 0.5 mol%, b is 0 to 0.20 mol%, and Nb is2O5、La2O3、Sm2O3、Nd2O3One or more of the compounds is a semiconducting agent; al (Al)2O3And TiO2The process adopted as the sintering aid comprises the following steps: pressing the above listed materials into a wafer in an atmospheric atmosphere at 1250-1380 ℃Sintering is carried out for 10-30 minutes under the condition of heat preservation, so that the sintering is fully carried out and solid-phase reaction is realized; and grinding the surface of the sintered wafer, and putting an electrode on the wafer to obtain the PTCR ceramic material. The ceramic material has room temperature resistivity as low as 30 omega cm, Curie temperature Tc as high as 155 deg.c and lift-to-drag ratio as high as 106The above.

Description

Preparation method of high-Tc low-resistance lead-free PTC material
Technical Field
The invention relates to a high Curie temperature (Tc) for sintering in atmospheric atmosphere>150 deg.C), high lift-drag ratio (R)max/Rmin>1.0×106) Low room temperature resistivity (ρ: about 30 omega cm) lead-free positive temperature coefficient thermistor ceramic.
Background
Ferroelectric BaTiO3Curie temperature T ofCAt 120 deg.C, it can be made semiconductive while having a positive temperature coefficient thermistor effect (PTC effect) by adding a proper amount of donor impurities. The PTC material has wide application in the fields of automobiles, household appliances, communication, automatic control and the like. The PTC heating elements widely used at present all adopt BaTiO3-PbTiO3System, TCThe higher the material isThe more lead content. The PTC element for heating the air conditioner with the largest dosage has the Curie temperature of about 250 ℃ and the content of PbO in the element exceeds 30 wt%. As is well known, heavy metal element Pb has toxic action on human body and has a strong influence on environment. It is estimated that 1 gram of lead causes soil pollution of 1 square meter, which is long-term, and disposal of lead-containing PTC elements in future will be a major problem. Therefore, the development of the lead-free PTC material with high Tc temperature has important significance for the current economic and social development.
The lead-free research of PTCR materials started in the last 80 th century with ferroelectric (Na, Bi) TiO3(BNT for short) and BaTiO3Solid solution to obtain (Ba, Bi, Na) TiO3Is a high temperature PTCR material. BNT is a relaxation-type ferroelectric with a complex perovskite structure with a curie temperature of 320 ℃. Research shows that sintering is carried out in an atmospheric atmosphere along with (Na, Bi) TiO3The increase in the amount of solid solution causes the room temperature resistivity of the PTC material to sharply increase to insulation. In a non-oxidizing atmosphere such as N2Or sintering in a reducing atmosphere, the resistivity of the PTCR material can still meet the practical requirements even if the BNT content reaches 30mol percent. But the sintering manufacturing method requiring atmosphere protection increases the process cost. The invention is to be realized in BNT-BaTiO3Introducing a third element CaTiO on the basis of a binary system PTCR material3And adding Li2CO3As a sintering aid, the material is prepared by sintering in the atmosphere, the room temperature resistivity is about 30 omega cm, the Curie temperature is about 150 ℃, and the lift-drag ratio is up to 106The above lead-free PTC material.
Disclosure of Invention
The invention aims to provide a high Curie temperature (Tc) for sintering in an atmospheric atmosphere>150 deg.C), high lift-drag ratio (R)max/Rmin>1.0×106) Low room temperature resistivity (ρ: about 30 omega cm) lead-free positive temperature coefficient thermistor ceramic.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of lead-free positive temperature coefficient thermistor ceramic is characterized by comprising the following specific steps:
a. x (Bi)1/2Na1/2)TiO3-yCaTiO3-(1-x-y)BaTiO3+aLi2CO3+bSb2O3A powder wherein x is 0.01 to 0.12, y is 0 to 0.20, a is 0 to 0.5 mol%, b is 0 to 0.20 mol%, and Nb is2O5、La2O3、 Sm2O3、Nd2O3One or more of the compounds is a semiconducting agent, and the doping amount is 0.05-0.50 atom% of the material; further doping 0-0.50 atom% Al2O3And 0 to 3.5 atom% of TiO2Taking agate balls and alcohol or deionized water as media, performing ball milling for 12-72 hours, and drying to obtain mixed powder;
b. adding 10wt% PVA water solution (PVA: polyvinyl alcohol) which accounts for 3.0-12.0 wt% of the weight of the mixed powder obtained in the step a into the mixed powder, and granulating;
c. pressing the particles obtained in the step b into round pieces;
d. and (c) preserving the temperature of the wafer obtained in the step (c) at 1250-1380 ℃ for 10-30 minutes to obtain the lead-free positive temperature coefficient thermistor ceramic.
The semiconducting agent is Nb2O5、La2O3、Sm2O3、Nd2O3At least one of the compounds.
The CaTiO described above3And (Bi)1/2Na1/2)TiO3The powder is obtained by the following method: by atomic ratio of Bi2O3：Na2O： TiO20.5: 0.5: 1.0 and CaCO in atomic ratio3：TiO21.0: weighing two groups of analytically pure raw materials according to the proportion of 1.0, mixing the two groups of raw materials respectively by taking agate balls and alcohol as media, ball-milling the mixture in a mill for 3-72 hours, and calcining the dried mixture at 980 ℃ and 1400 ℃ for 0.5-4.0 hours to obtain (Bi) respectively1/2Na1/2)TiO3And CaTiO3And (3) powder.
Compared with the prior art, the invention has the beneficial effects that: the invention is in the airThe electrical properties of the PTCR lead-free ceramic material prepared in a gas atmosphere can meet the following parameter requirements: curie temperature Tc>Resistivity at 150 ℃ at room temperature<30 omega cm, PTC lift-drag ratio Rmax/Rmin>1.8×106Temperature coefficient of resistance α>34％/℃。
Drawings
FIG. 1.BNT 4.0 mol% and Ca2+R-T curve of 0-20 mol% sample;
FIG. 2.BNT 6.0 mol% and Ca2+R-T curve of 0-20 mol% sample; (ii) a
FIG. 3 shows that BNT is 4.0 mol% and Ca2+＝6.0mol％、Li+R-T curve of 0-0.3 mol% sample;
FIG. 4. samples with different Sb contents (Sb)3+0 to 0.15 mol%) of the R-T curve of the sample.
Detailed Description
The present invention will be described in further detail with reference to the following specific examples.
Example 1
According to the weight ratio of 0.04 (Bi)1/2Na1/2)TiO3-yCaTiO3-(0.96-y)BaTiO3+0.165mol％Nb2O5+0.167mol％Al2O3+1.0mol％TiO2+0.2mol％Li2CO3The compounding is carried out, wherein y is 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18 and 0.20, and the weight is calculated according to the molar ratio in the formula, and the weighed mass is as shown in the following table 1:
TABLE 1 ingredient TABLE I (Unit: g)
Numbering BNT BaTiO3 CaTiO3 Nb2O5 Al2O3 TiO2 Li2CO3
B4-C-00 8.4740 223.8645 0 0.4386 0.1703 0.7987 0.1478
B4-C-02 8.4740 219.2007 2.7189 0.4386 0.1703 0.7987 0.1478
B4-C-04 8.4740 214.5368 5.4377 0.4386 0.1703 0.7987 0.1478
B4-C-06 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478
B4-C-08 8.4740 205.2091 10.8755 0.4386 0.1703 0.7987 0.1478
B4-C-10 8.4740 200.5453 13.5944 0.4386 0.1703 0.7987 0.1478
B4-C-12 8.4740 195.8814 16.3132 0.4386 0.1703 0.7987 0.1478
B4-C-14 8.4740 191.2176 19.0321 0.4386 0.1703 0.7987 0.1478
B4-C-16 8.4740 186.5538 21.7510 0.4386 0.1703 0.7987 0.1478
B4-C-18 8.4740 181.8899 24.4698 0.4386 0.1703 0.7987 0.1478
B4-C-20 8.4740 177.2261 27.1887 0.4386 0.1703 0.7987 0.1478
Weighing according to the formula in the first ingredient table, and pre-synthesizing BNT and CaTiO3Then adding BaTiO in proportion3、 Nb2O5、Al2O3、TiO2、Li2CO3Using agate balls and deionized water as media, performing ball milling for 24 hours, adding 8 wt% of 10wt% polyvinyl alcohol (PVA) into dried powder for granulation, pressing a wafer with the diameter of 10 multiplied by 2.0mm under the pressure of 10MPa, maintaining the pressure for 15s, sintering the pressed wafer in the air atmosphere, wherein the sintering temperature is 1350 ℃, and preserving the temperature for 10min at the temperature to fully sinter the wafer and realize solid-phase reaction; and (3) after the surface of the sintered sample is polished to be smooth, washing for 8min in ultrasonic waves, coating with an Ag-Zn slurry electrode, sintering and insulating the electrode at 490 ℃ for 8min, and curing the electrode to finally obtain the PTCR ceramic sample. The ceramic sample was heated at a temperature rise rate of 2 ℃/min, and the resistance-temperature characteristics thereof were measured, and the results are shown in table 2 and fig. 1.
TABLE 2 Electrical Properties of samples of different Ca contents
Figure BDA0002345423230000041
And (4) conclusion: introduction of third element CaTiO3The temperature resistivity of the sample chamber can be greatly reduced, and the PTC effect of the material is improved. Ca2+At a content of 0.06mol, the PTC properties are best: the resistivity at room temperature is as low as 36 omega cm, the Curie temperature reaches 148 ℃, the lift-to-drag ratio reaches 1.87E +06, and the nonlinear coefficient is about 16.8 percent
Example 2
According to 0.06 (Bi)1/2Na1/2)TiO3-yCaTiO3-(0.94-y)BaTiO3+0.165mol％Nb2O5+0.167mol％Al2O3+1.0mol％TiO2+0.2mol％Li2CO3To carry outThe ingredients, y ═ 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, were weighed out after weighing in terms of molar ratios in the formula, and the weights were as given in table 3 below:
TABLE 3 ingredient TABLE II (Unit: g)
Figure BDA0002345423230000042
Figure BDA0002345423230000051
Weighing according to the formula in the second ingredient table, and pre-synthesizing BNT and CaTiO3Then adding BaTiO in proportion3、 Nb2O5、Al2O3、TiO2、Li2CO3Using agate balls and deionized water as media, performing ball milling for 24 hours, adding 8 wt% of polyvinyl alcohol (PVA) with the concentration of 10wt% into dried powder for granulation, pressing a wafer with the diameter of 10 multiplied by 2.0mm under the pressure of 10MPa, maintaining the pressure for 15s, sintering the pressed wafer in the air atmosphere, wherein the sintering temperature is 1330 ℃, and preserving the temperature for 10min at the temperature to fully sinter the wafer and realize solid-phase reaction; and (3) after the surface of the sintered sample is polished to be smooth, washing for 8min in ultrasonic waves, coating with an Ag-Zn slurry electrode, sintering and insulating the electrode at 490 ℃ for 8min, and curing the electrode to finally obtain the PTCR ceramic sample. The ceramic sample was heated at a temperature rise rate of 2 ℃/min, and the resistance-temperature characteristics thereof were measured, and the results are shown in table 4 and fig. 2.
TABLE 4 Electrical Properties of BNT content 0.06 sample
Figure BDA0002345423230000052
And (4) conclusion: with Ca2+The resistivity at room temperature is increased, and the Curie temperature and the lift-drag ratio are reduced. As can be seen, Ca2+At a content of 0.02mol, the PTC properties are best: the resistivity at room temperature is as low as 176 omega cm, the Curie temperature reaches 154 ℃, the lift-to-drag ratio reaches 8.98E +05, and the nonlinear coefficient is about 24.2 percent. Same as in example 1In comparison, the Curie temperature of the material increased by 6 ℃ and the room temperature resistance increased by about 5 times.
Example 3
According to the weight ratio of 0.04 (Bi)1/2Na1/2)TiO3-0.06CaTiO3-0.90BaTiO3+aLi2CO3+0.165 mol％Nb2O5+0.167mol％Al2O3+1.0mol％TiO2And (3) preparing materials, wherein a is 0-0.003, weighing the materials according to the molar ratio in the molecular formula, and weighing the materials according to the following table 5:
TABLE 5 ingredient table III (unit: g)
Numbering BNT BaTiO3 CaTiO3 Nb2O5 Al2O3 TiO2 Li2CO3
L-00 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0
L-01 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.0739
L-02 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478
L-03 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.2217
Weighing according to the formula in the third ingredient table, and pre-synthesizing BNT and CaTiO3Then adding BaTiO in proportion3、 Nb2O5、Al2O3、TiO2、Li2CO3Using agate balls and deionized water as media, performing ball milling for 24 hours, adding 8 wt% of 10wt% polyvinyl alcohol (PVA) into dried powder for granulation, pressing a wafer with the diameter of 10 multiplied by 2.0mm under the pressure of 10MPa, maintaining the pressure for 15s, sintering the pressed wafer in the air atmosphere, wherein the sintering temperature is 1350 ℃, and preserving the temperature for 10min at the temperature to fully sinter the wafer and realize solid-phase reaction; and (3) after the surface of the sintered sample is polished to be smooth, washing for 8min in ultrasonic waves, coating with an Ag-Zn slurry electrode, sintering and insulating the electrode at 490 ℃ for 8min, and curing the electrode to finally obtain the PTCR ceramic sample. The resistance-temperature characteristics of the ceramic samples were measured by heating the ceramic samples at a temperature rise rate of 2 ℃/min, and the results are shown in table 6 and fig. 3.
TABLE 6 Electrical Properties of samples of different Li contents
Figure BDA0002345423230000061
Figure BDA0002345423230000071
And (4) conclusion: addition of Li2CO3So that the sample has good PTC performance. As the Li content increases, the room temperature resistance increases and the nonlinear coefficient decreases. Taken together, the best sample performance is obtained with a Li content of about 0.2 mol%: the resistivity at room temperature is as low as 36 omega cm, the Curie temperature and the lift-drag ratio are respectively as high as 148 ℃ and 1.87E +06, and the nonlinear coefficient is about 16.8 percent
Example 4
According to the weight ratio of 0.04 (Bi)1/2Na1/2)TiO3-0.06CaTiO3-0.90BaTiO3+0.2mol％Li2CO3+bSb2O3+0.165mol％Nb2O5+0.167mol％Al2O3+1.0mol％TiO2And (3) mixing, wherein b is 0-0.15 mol%, and weighing after calculating the weight according to the molar ratio in the molecular formula, wherein the weighing mass is as shown in the following table 7:
TABLE 7 ingredient TABLE IV (Unit: g)
Numbering BNT BaTiO3 CaTiO3 Nb2O5 Al2O3 TiO2 Li2CO3 Sb2O3
S-00 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0
S-01 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.0029
S-02 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.0875
S-03 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.1460
S-04 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.2040
S-05 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.2915
S-06 8.4740 209.8730 8.1566 0.4386 0.1703 0.7987 0.1478 0.4375
Weighing according to the formula in the fourth ingredient table, and pre-synthesizing BNT and CaTiO3Then adding BaTiO in proportion3、 Nb2O5、Al2O3、TiO2、Li2CO3、Sb2O3Using agate balls and deionized water as media, performing ball milling for 24 hours, adding 8 wt% of polyvinyl alcohol (PVA) with the concentration of 10wt% into dried powder for granulation, pressing a wafer with the diameter of 10 multiplied by 2.0mm under the pressure of 10MPa, maintaining the pressure for 15s, sintering the pressed wafer in the air atmosphere, wherein the sintering temperature is 1330 ℃, and preserving the temperature for 10min at the temperature to fully sinter the wafer and realize solid-phase reaction; and (3) after the surface of the sintered sample is polished to be smooth, washing for 8min in ultrasonic waves, coating with an Ag-Zn slurry electrode, sintering and insulating the electrode at 490 ℃ for 8min, and curing the electrode to finally obtain the PTCR ceramic sample. At 2 deg.C/miThe ceramic sample was heated at the temperature increase rate of n, and the resistance-temperature characteristics thereof were measured, and the results are shown in table 8 and fig. 4.
TABLE 8 different Sb2O3Electrical properties of the content samples
Figure BDA0002345423230000081
And (4) conclusion: the above samples were sintered at 1330 ℃ from which it can be seen that a small amount of Sb was added2O3The method is beneficial to reducing the sintering temperature and improving the PTC performance of the sample. Wherein Sb2O3When the content is 0.01 mol%, the PTC performance of the sample is best, the room temperature resistivity is as low as 33 omega cm, the Curie temperature reaches 146 ℃, the lift-to-drag ratio is as high as 4.02E +05, and the nonlinear coefficient is about 17.1%.

Claims (3)

1. A preparation method of low-resistance lead-free positive temperature coefficient thermistor ceramic is characterized by comprising the following specific steps:
a. will be provided withx(Bi1/2Na1/2)TiO3-yCaTiO3-(1-x-y)BaTiO3+aLi2CO3+bSb2O3A powder, wherein,x=0.01~0.12,y=0~0.20,a=0～0.5 mol%,b=0～0.20 mol%；Nb2O5、La2O3、Sm2O3、Nd2O3one or more compounds are used as a semiconducting agent, and the doping amount of the compound is 0.05-0.50 atom% of the material; further doping 0-0.50 atom% Al2O3And 0 to 3.5 atom% of TiO2Taking agate balls and alcohol or deionized water as media, performing ball milling for 12-72 hours, and drying to obtain mixed powder;
b. adding 10wt% PVA water solution (PVA: polyvinyl alcohol) which accounts for 3.0-12.0 wt% of the weight of the mixed powder obtained in the step a into the mixed powder, and granulating;
c. pressing the particles obtained in the step b into round pieces;
d. and (c) preserving the temperature of the wafer obtained in the step (c) at 1250-1380 ℃ for 10-30 minutes to obtain the lead-free positive temperature coefficient thermistor ceramic.
2. The method of claim 1, wherein the semiconducting agent is Nb2O5、La2O3、Sm2O3、Nd2O3At least one of the compounds.
3. The method of claim 1 wherein the CaTiO is a ceramic material having a positive temperature coefficient3And (Bi)1/2Na1/2)TiO3The powder is obtained by the following method: by atomic ratio of Bi2O3：Na2O：TiO20.5: 0.5: 1.0 and CaCO in atomic ratio3：TiO21.0: weighing two groups of analytically pure raw materials according to the proportion of 1.0, mixing the two groups of raw materials respectively by taking agate balls and alcohol as media, ball-milling the mixture in a mill for 3-72 hours, and calcining the dried mixture at 980 ℃ and 1400 ℃ for 0.5-4.0 hours to obtain (Bi) respectively1/2Na1/2)TiO3And CaTiO3And (3) powder.
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Publication number Priority date Publication date Assignee Title
CN114907106A (en) * 2022-03-30 2022-08-16 电子科技大学 Preparation method of high-mechanical-strength wide-temperature wide-band MnZn power ferrite
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