Wide-temperature-range negative temperature coefficient thermosensitive ceramic material and preparation method thereof

Abstract

The application relates to a wide-temperature-range negative temperature coefficient thermosensitive ceramic material and a preparation method thereof. The thermosensitive ceramic material comprises, in percentage by weight, 58.17-71.47% of lanthanum trioxide, 20.53-23.01% of aluminum trioxide, 3.98-15.36% of cerium dioxide and 1.54-5.94% of niobium pentoxide, and the chemical composition is La 1‑ x Ce x Al 1‑y Nb y O3, wherein x=0.05-0.20 and y=0.025-0.10. The NTC thermistor has the advantages of an ultra-wide temperature range (25 DEG C-1500 DEG C), good consistency of resistance value and B value, a resistance drift rate of less than 0.375% after aging for 500 hours at high temperature, high stability, long service life and the like.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a novel wide-temperature-range negative temperature coefficient thermistor ceramic material and its preparation method. Background Technology

[0002] NTC materials are semiconductor ceramics made from two or more metal oxides such as manganese, copper, silicon, cobalt, iron, nickel, and zinc through processes such as thorough mixing, molding, and sintering. They can be used to create thermistors with a negative temperature coefficient (NTC). A characteristic of NTC is that its resistance decreases non-linearly as the bulk temperature increases. The resistivity and material constant of this material vary depending on the proportion of material components, sintering atmosphere, sintering temperature, and structural state. Furthermore, NTC thermistor materials represented by non-oxide materials such as silicon carbide, tin selenide, and tantalum nitride have also emerged. These materials achieve miniaturization while exhibiting small resistance-temperature fluctuations and fast response to various temperature changes, making them suitable for use as high-sensitivity, high-precision temperature sensors. They are also frequently used in electronic circuits for real-time temperature monitoring and temperature compensation.

[0003] Current research on NTC materials involves diverse material systems, commonly including spinel, perovskite, and pyrochlore structures. Spinel materials are primarily used for low-temperature measurements, perovskite materials for medium- and high-temperature measurements, and pyrochlore materials for high- and ultra-high-temperature measurements. Given the current research status, developing a novel, ultra-wide-temperature-range NTC material that covers both low and high-temperature regions is essential for practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a novel wide-temperature-range negative temperature coefficient thermistor ceramic material and its preparation method. This material uses lanthanum trioxide, aluminum trioxide, cerium dioxide, and niobium pentoxide as raw materials, which are mixed, ground, calcined, cold isostatically pressed, sintered at high temperature, and coated with electrodes to obtain a material constant of B. 25℃ / 1500℃ This is a wide-temperature-range negative temperature coefficient thermistor ceramic material with a resistivity of 1100.93-73032.65 Ω•cm at 1000℃ and a temperature range of 4568.92-18175.1 K. This resistive material exhibits stable performance and good consistency, displaying a significant negative temperature coefficient characteristic within the temperature range of 25℃-1500℃, making it suitable for manufacturing wide-temperature-range thermistor elements.

[0005] This invention provides a wide-temperature-range negative temperature coefficient thermistor ceramic material, wherein the thermistor ceramic material comprises, by weight percentage: 58.17-71.47% lanthanum trioxide, 20.53-23.01% aluminum trioxide, 3.98-15.36% cerium dioxide, and 1.54-5.94% niobium pentoxide, and its chemical composition is La. 1-x Ce x Al 1-y Nb y O3, where x = 0.05 - 0.20, y = 0.025 - 0.10.

[0006] Preferably, the constant of the thermistor ceramic material is B. 25℃ / 1500℃ =4568.92-18175.1K, resistivity at 1000℃ is 1100.93-73032.65Ω•cm.

[0007] This invention provides a method for preparing a wide-temperature-range negative temperature coefficient thermistor ceramic material, comprising the following steps:

[0008] a. Weigh out lanthanum trioxide, aluminum trioxide, cerium dioxide and niobium pentoxide and mix them to obtain a mixture powder;

[0009] b. Calcine and grind the mixture powder from step a to obtain La. 1-x Ce x Al 1-y Nb y O3 powder;

[0010] c. The La obtained in step b 1-x Ce x Al 1-y Nb y O3 powder is pressed into blocks, the formed blocks are cold isostatically pressed, and then sintered to obtain thermistor ceramic materials.

[0011] d. Coat the electrode with the thermistor ceramic material obtained in step c, and then anneal it to obtain a wide-temperature-range negative temperature coefficient thermistor ceramic material with negative temperature coefficient characteristics in the temperature range of 25℃-1500℃.

[0012] Preferably, in step a, the mixture is ground for 6-10 hours to obtain a powder.

[0013] Preferably, in step b, the calcination temperature is 1200-1300℃, the calcination time is 10-20 hours, and the grinding time is 6-8 hours.

[0014] Preferably, in step c, the pressure for forming the briquette is 10-20 kg / cm². 2The pressing time is 0.8-1.5 min, followed by cold isostatic pressing, holding the pressure at 250-350 MPa for 3-5 min, sintering temperature at 1500-1600℃, and sintering time at 15-20 hours.

[0015] Preferably, in step d, platinum paste electrodes are coated on both sides and then annealed at 800-900°C for 30-60 minutes.

[0016] Specifically, the novel wide-temperature-range negative temperature coefficient thermistor ceramic material described in this invention is made from raw materials comprising 58.17-71.47% lanthanum trioxide, 20.53-23.01% aluminum trioxide, 3.98-15.36% cerium dioxide, and 1.54-5.94% niobium pentoxide by weight percentage, and its chemical composition is La. 1-x Ce x Al 1-y Nb y O3, where x = 0.05-0.20, y = 0-0.10; the resulting material constant is B. 25℃ / 1500℃ =4568.92-18175.1K, resistivity at 1000℃ is 1100.93-73032.65Ω•cm. The specific operation should be carried out according to the following steps:

[0017] a. Weigh out 58.17-71.47% lanthanum trioxide, 20.53-23.01% aluminum trioxide, 3.98-15.36% cerium dioxide, and 1.54-5.94% niobium pentoxide by weight percentage and mix them. Place the mixture in an agate mortar and grind it for 6-10 hours to obtain powder.

[0018] b. Calcine the powder ground in step a at 1300℃ for 10 hours, then grind it for another 6 hours to obtain La. 1- x Ce x Al 1-y Nb y O3 powder;

[0019] c. The powder material obtained in step b is processed at a concentration of 10-20 kg / cm³. 2 The material is pressed into blocks under pressure for 0.8-1.5 minutes. The formed block material is then subjected to cold isostatic pressing at a pressure of 250-350 MPa for 3 minutes, and then sintered at 1550℃ for 15 hours to obtain a wide temperature range thermistor ceramic material.

[0020] d. Coat both sides of the ceramic material sintered in step c with platinum paste electrodes, and then anneal at 900℃ for 30 minutes to obtain a material with a negative temperature coefficient characteristic in the temperature range of 25℃-1500℃, and a material constant of B.25℃ / 1500℃ =4568.92-18175.1K, with a resistivity of 1100.93-73032.65Ω•cm over a wide temperature range.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention successfully developed a negative temperature coefficient thermistor material with an ultra-wide temperature range, applicable to environments from room temperature to ultra-high temperatures, effectively expanding the application areas of this material system. This material system can cope with different external temperature environments, reducing the need to replace sensors due to temperature limitations in practical use, and lowering actual operating costs. Furthermore, this material system does not use heavy metals or other chemical raw materials, making the formulation green and environmentally friendly. Attached Figure Description

[0023] Figure 1 The XRD pattern of this invention shows that as the content of cerium dioxide and niobium pentoxide increases, the diffraction peaks of all samples can match the perovskite structure of LaAlO3 well, and no second phase is generated, indicating that cerium and niobium have been successfully doped into the LaAlO3 phase.

[0024] Figure 2 La, a sample obtained by cerium-niobium co-doping 1-x Ce x The resistance-temperature relationship diagram of AlO3 shows the temperature response of La after sintering. 1- x Ce x Al 1-y Nb y The graph shows the relationship between the logarithm of the resistivity (ρ) of LaAlO3 ceramics (lnρ) and the reciprocal of temperature (1000 / T). It can be seen that in the undoped LaAlO3 material, lnρ decreases with increasing 1000 / T in the temperature range of 450℃-1400℃, exhibiting a negative temperature coefficient behavior. However, the material constant B and resistivity at 1000℃ of LaAlO3 are relatively large, making it difficult to apply in the NTC field. Doping with cerium significantly improves the resistivity of LaAlO3. 1-x Ce x The temperature range of AlO3 ceramic materials is broadened to between 25℃ and 1500℃. 1- x Ce x Al 1-y Nb y In the temperature range of 25℃-1500℃, the lnρ of O3 material decreases with increasing 1000 / T, exhibiting a negative temperature coefficient behavior. Furthermore, it significantly reduces the material constant B and the resistivity at 1000℃, and the reduction in both the material constant B and the resistivity at 1000℃ is positively correlated with the doping concentration. 1-xCe x Al 1-y Nb y O3 material has emerged as a negative temperature coefficient thermistor ceramic material applicable to wide-temperature-range temperature measurement, and is expected to be used in temperature measurement in some special high-temperature environments such as aviation and deep sea. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] The specific preparation method of the present invention is as follows: S1. Weighing materials; S2. Mixing; S3. Grinding; S4. Pre-sintering; S5. Secondary grinding; S6. Pressing into tablets; S7. Isostatic pressing; S8. Sintering; S9. Coating with platinum paste; S10. Annealing; S11. Welding leads.

[0027] Example 1

[0028] a. According to La 0.95 Ce 0.05 Al 0.975 Nb 0.025 The stoichiometric ratio of O3 was determined by weighing 71.48% lanthanum trioxide, 23.01% aluminum trioxide, 3.98% cerium dioxide, and 1.54% niobium pentoxide by weight, and then mixing them. The mixture was then ground in an agate mortar for 6 hours to obtain powder.

[0029] b. Calcine the powder ground in step a at 1300℃ for 10 hours, then grind it for another 6 hours to obtain La. 0.95 Ce 0.05 Al 0.975 Nb 0.025 O3 powder;

[0030] c. The powder material obtained in step b is processed at a concentration of 10 kg / cm³. 2 The material is pressed into blocks under pressure for 0.8 minutes. The formed block material is then subjected to cold isostatic pressing at a pressure of 250 MPa for 3 minutes, and then sintered at 1550℃ for 15 hours to obtain a high-temperature thermistor ceramic material.

[0031] d. Coat both sides of the ceramic material sintered in step c with platinum paste electrodes, and then anneal at 900℃ for 30 minutes to obtain a material with a negative temperature coefficient characteristic in the temperature range of 250℃-1200℃, and a material constant of B. 200℃ / 1400℃ =6287.52K, resistivity of 73032.65Ω•cm in the medium and high temperature range, is a negative temperature coefficient thermistor ceramic material.

[0032] Example 2

[0033] a. According to La0.9 Ce 0.1 Al 0.95 Nb 0.05 The stoichiometric ratio of O3 was determined by weighing 66.94% lanthanum trioxide, 22.17% aluminum trioxide, 7.59% cerium dioxide, and 3.04% niobium pentoxide by weight, and then mixing them. The mixture was then ground in an agate mortar for 8 hours to obtain powder.

[0034] b. Calcine the powder ground in step a at 1250℃ for 10 hours, then grind it for another 7 hours to obtain La. 0.9 Ce 0.1 AlO3 powder;

[0035] c. The powder material obtained in step b is processed at 15 kg / cm³. 2 The material is pressed into blocks under pressure for 1.5 minutes. The formed block material is then subjected to cold isostatic pressing at a pressure of 350 MPa for 3 minutes, and then sintered at a temperature of 1550℃ for 15 hours to obtain a high-temperature thermistor ceramic material.

[0036] d. Coat both sides of the ceramic material sintered in step c with platinum paste electrodes, and then anneal at 900℃ for 30 minutes to obtain a material with a negative temperature coefficient characteristic in the temperature range of 200℃-1300℃, and a material constant of B. 200℃ / 1400℃ =5457.54K, resistivity of 10906.67Ω•cm in the medium and high temperature range, a thermistor material with a negative temperature coefficient.

[0037] Example 3

[0038] a. According to La 0.8 Ce 0.2 Al 0.9 Nb 0.1 The stoichiometric ratio of O3 was determined by weighing 58.17% lanthanum trioxide, 20.53% aluminum trioxide, 15.359% cerium dioxide, and 5.94% niobium pentoxide by weight, and then mixing them. The mixture was then ground in an agate mortar for 9 hours to obtain powder.

[0039] b. Calcine the powder ground in step a at 1300℃ for 10 hours, then grind it for another 8 hours to obtain La. 0.8 Ce 0.2 Al 0.9 Nb 0.1 O3 powder;

[0040] c. The powder material obtained in step b is processed at 18 kg / cm³. 2The material is pressed into blocks under pressure for 1.2 minutes. The formed block material is then subjected to cold isostatic pressing at a pressure of 300 MPa for 4 minutes, and then sintered at 1550℃ for 18 hours to obtain a high-temperature thermistor ceramic material.

[0041] d. Coat both sides of the ceramic material sintered in step c with platinum paste electrodes, and then anneal at 850℃ for 30 minutes to obtain a material with a negative temperature coefficient characteristic in the temperature range of 25℃-1500℃, and a material constant of B. 200℃ / 1400℃ =4568.92K, resistivity of 1100.93Ω•cm in the medium and high temperature range, a thermistor material with a negative temperature coefficient.

[0042] Example 4 (Comparative)

[0043] a. Weigh out 15.222 parts of lanthanum trioxide and 4.778 parts of aluminum trioxide according to the stoichiometric ratio of LaAlO3 and mix them. Place the mixed raw materials in an agate mortar and grind for 8 hours to obtain powder.

[0044] b. Calcine the powder ground in step a at 1300℃ for 10 hours, and then grind it for 6 hours to obtain LaAlO3 powder.

[0045] c. The powder material obtained in step b is processed at a concentration of 20 kg / cm³. 2 The pressure is used to press the material into blocks for 2 minutes. The formed block material is then subjected to cold isostatic pressing at a pressure of 300 MPa for 3 minutes. Finally, it is sintered at 1600℃ for 20 hours to obtain perovskite-type medium-high temperature thermistor ceramic material.

[0046] d. Coat both sides of the sintered thermistor ceramic material from step c with platinum paste electrodes, and then anneal at 900℃ for 30 minutes to obtain a material with a negative temperature coefficient characteristic in the temperature range of 450℃-1400℃, and a material constant of B. 450℃ / 1400℃ =18175.1K, resistivity of 68971.87Ω•cm at 1000℃, and aging coefficient of 1.038% after 500 hours of aging at 1000℃.

[0047] Example 5

[0048] Compare any of the negative temperature coefficient thermistor ceramic materials obtained in the medium-high temperature region of Examples 1-3 with that in Example 4, see [link to example]. Figure 1 The results showed that as the content of cerium dioxide and niobium pentoxide increased, the diffraction peaks of all samples matched the perovskite structure of LaAlO3 well, and no second phase was formed, indicating that cerium and niobium were successfully doped into the LaAlO3 phase.

[0049] Figure 2 La, a sample obtained by cerium-niobium co-doping 1-x Ce x The resistance-temperature relationship diagram of AlO3 shows the temperature response of La after sintering. 1- x Ce x Al 1-y Nb y The graph shows the relationship between the logarithm of the resistivity (ρ) of LaAlO3 ceramics (lnρ) and the reciprocal of temperature (1000 / T). It can be seen that in the undoped LaAlO3 material, lnρ decreases with increasing 1000 / T in the temperature range of 450℃-1400℃, exhibiting a negative temperature coefficient behavior. However, the material constant B and resistivity at 1000℃ of LaAlO3 are relatively large, making it difficult to apply in the NTC field. Doping with cerium significantly improves the resistivity of LaAlO3. 1-x Ce x The temperature range of AlO3 ceramic materials is broadened to between 25℃ and 1500℃. 1- x Ce x Al 1-y Nb y In the temperature range of 25℃-1500℃, the lnρ of O3 material decreases with increasing 1000 / T, exhibiting a negative temperature coefficient behavior. Furthermore, it significantly reduces the material constant B and the resistivity at 1000℃, and the reduction in both the material constant B and the resistivity at 1000℃ is positively correlated with the doping concentration. 1-x Ce x Al 1-y Nb y O3 material has emerged as a negative temperature coefficient thermistor ceramic material applicable to wide-temperature-range temperature measurement, and is expected to be used in temperature measurement in some special high-temperature environments such as aviation and deep sea.

[0050] The NTC thermistor of the present invention has an ultra-wide temperature range (25℃~1500℃), good consistency between resistance value and B value, and a resistance drift rate of less than 0.375% after aging at high temperature for 500 hours. It has high stability and long service life. In addition, the powder particles prepared by the present invention have high dispersion, are not prone to agglomeration, and have high chip strength.

[0051] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values ​​of the present invention can all achieve this method, and examples are not listed here.

[0052] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A wide-temperature-range negative temperature coefficient thermistor ceramic material, characterized in that, The thermistor ceramic material is made from lanthanum trioxide (58.17-66.94% by weight), aluminum trioxide (20.53-22.17%), cerium dioxide (7.59-15.36%), and niobium pentoxide (3.04-5.94%) as raw materials, and its chemical composition is La. 1-x Ce x Al 1-y Nb y O3, where x = 0.10 ~ 0.20, y = 0.05 ~ 0.

10.

2. A method for preparing the wide-temperature-range negative temperature coefficient thermistor ceramic material according to claim 1, comprising the following steps: a. Weigh out lanthanum trioxide, aluminum trioxide, cerium dioxide and niobium pentoxide and mix them to obtain a mixture powder; b. calcining the mixture powder in step a, grinding to obtain La 1-x Ce x Al 1-y Nb y O3 powder; c. compressing the La 1-x Ce x Al 1-y Nb y O3 powder to form a block, cold isostatic pressing the block, and then sintering to obtain a heat-sensitive ceramic material. d. Coat the electrode with the thermistor ceramic material obtained in step c, and then anneal it to obtain a wide-temperature-range negative temperature coefficient thermistor ceramic material with negative temperature coefficient characteristics in the temperature range of 25℃~1500℃.

3. The preparation method according to claim 2, characterized in that, In step a, the mixture is ground for 6 to 10 hours to obtain a powder.

4. The preparation method according to claim 2, characterized in that, In step b, the calcination temperature is 1200 ~ 1300℃, the calcination time is 10 ~ 20 hours, and the grinding time is 6 ~ 8 hours.

5. The preparation method according to claim 2, characterized in that, In step c, the pressure for briquetting is 10~20 kg / cm². 2 The pressing time is 0.8 to 1.5 minutes, followed by cold isostatic pressing at a pressure of 250 to 350 MPa for 3 to 5 minutes, sintering temperature of 1500 to 1600℃, and sintering time of 15 to 20 hours.

6. The preparation method according to claim 2, characterized in that, In step d, platinum paste electrodes are coated on both sides and then annealed at 800-900℃ for 30-60 minutes.

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