CaCeNbWO8-based high-entropy negative temperature coefficient thermal sensitive ceramic material and preparation method thereof

Abstract

The invention discloses a CaCeNbWO8-based high-entropy negative temperature coefficient thermal sensitive ceramic material and a preparation method thereof, belongs to the field of negative temperature coefficient thermistors, and aims to expand the temperature zone range of a scheelite structure negative temperature coefficient thermal sensitive ceramic material. The material is prepared by mixing and firing raw materials including calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, samarium oxide, europium oxide, lanthanum trioxide, holmium oxide or dysprosium oxide according to a stoichiometric ratio, the chemical formula is (Ca1 / 3Ce1 / 3M1 / 3) (Nb1 / 2W1 / 2) O4, and M is Sm, Eu, La, Ho or Dy; the electrical property parameters of the thermal sensitive ceramic material with the negative temperature coefficient are as follows: B200 DEG C / 1100 DEG C is equal to 6081-7210 + / -1.8% K, rho1100 DEG C is equal to 2.87 * 10 < 3 >-4.09 * 10 < 3 > + / -1.37% omega.cm, and the applicable temperature range is 200-1100 DEG C. The material has a wide temperature range of 200-1100 DEG C, can maintain high sensitivity at a high temperature due to a large material constant B value, and shows excellent aging stability at 1000 DEG C. Through measurement, the resistance drift rate of the thermal sensitive ceramic material with the negative temperature coefficient is less than 3.49 + / -0.03% after the thermal sensitive ceramic material is aged at 1000 DEG C for 500 hours.

Description

Technical Field

[0001] The present application relates to the field of high-temperature thermistors, especially the field of negative temperature coefficient (NTC) thermistors, and specifically to a CaCeNbWO8-based high-entropy negative temperature coefficient thermistor ceramic material and its preparation method. Background Art

[0002] With the proposal of new quality productivity and the rapid development of new technologies, the demand for temperature monitoring in high-temperature operations such as high-temperature components of rocket and aircraft engines, battery management systems of new energy vehicles, and vehicle exhaust is increasing day by day. As a high-temperature measurement element, the negative temperature coefficient (NTC) thermistor has been widely used in the above fields. At the same time, with the continuous development of technology, higher requirements have been put forward for the temperature range, sensitivity, and high-temperature stability of NTC thermistors.

[0003] Ca-Ce-Nb-W-O-based ceramic materials with scheelite structure, as a currently widely studied and applied high-temperature NTC material, exhibit obvious NTC characteristics and good high-temperature structural stability at high temperatures; at the same time, their electrical properties are easily adjusted and modified; due to the existence of the above characteristics, they have broad application prospects in the field of high-temperature NTC thermistor ceramic materials. However, the existing Ca-Ce-Nb-W-O-based ceramic materials with scheelite structure have a low melting point and a small high-temperature resistivity, resulting in a maximum upper limit temperature of only 700 °C, which severely limits their application environment.

[0004] How to expand the temperature range of scheelite structure negative temperature coefficient thermistor ceramic materials has become an urgent technical problem to be solved. Summary of the Invention

[0005] The invention purpose of the present application is to provide a CaCeNbWO8-based high-entropy negative temperature coefficient thermistor ceramic material and its preparation method to expand the temperature range of scheelite structure negative temperature coefficient thermistor ceramic materials. This material has a relatively wide temperature range applicable to 200 °C to 1100 °C, and a large material constant B value enables it to maintain a high sensitivity at high temperatures and exhibit excellent aging stability at 1000 °C. It is measured that the resistance drift rate of this negative temperature coefficient thermistor ceramic material is less than 3.49 ± 0.03% after aging at 1000 °C for 500 hours.

[0006] A CaCeNbWO8-based high-entropy negative temperature coefficient thermistor ceramic material, whose chemical formula is (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4, where M is Sm, Eu, La, Ho or Dy.

[0007] The electrical property parameters of the negative temperature coefficient thermosensitive ceramic material are as follows: B 200℃ / 1100℃ = 6081 to 7210 ± 1.8% K, ρ 1100℃ = 2.87×10 3 ~ 4.09×10 3 ± 1.37% Ω·cm, and the applicable temperature range is 200°C to 1100°C. In short, the thermosensitive ceramic material has a negative temperature coefficient characteristic in the range of 200°C to 1100°C, and the material constant is B 200℃ / 1100℃ = 6081 to 7210 ± 1.8% K.

[0008] The negative temperature coefficient thermosensitive ceramic material is prepared by mixing and firing raw materials calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M; M is Sm, Eu, La, Ho or Dy.

[0009] The preparation method of the aforementioned CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material includes the following steps: a. According to the molar ratio of the chemical formula (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4, respectively weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M for mixing, ball milling, drying and then grinding to obtain the first powder; the oxide of M is samarium trioxide, europium trioxide, lanthanum trioxide, holmium trioxide or dysprosium trioxide; b. Calcinate and grind the first powder obtained in step a to obtain the second powder; c. Press the second powder obtained in step b into a block, and then perform cold isostatic pressing on the pressed block to obtain the third isostatic pressing block; sinter the third isostatic pressing block to obtain the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material.

[0010] It also includes the following steps: d. After coating platinum paste electrodes on both sides of the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material obtained in step c, anneal and then cool to room temperature to obtain a thermistor with a negative temperature coefficient characteristic in the temperature range of 200°C to 1100°C.

[0011] In the aforementioned step a, calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M are respectively weighed for mixing and ball milling; among them, the liquid phase dispersant for ball milling is ethanol, and the grinding medium is agate balls.

[0012] In the step a, the drying temperature is 60~100°C. Preferably, in the step a, the drying temperature is 100°C.

[0013] In the step a, the grinding time is 1~3h.

[0014] In the step b, the calcination temperature is 1000~1100°C and the calcination time is 3~5h.

[0015] In the step b, the first powder obtained in the step a is placed in a corundum crucible for calcination.

[0016] In the step b, the grinding operation is as follows: PVA solution is added to the calcined material as an organic binder, and the mixture is placed in an agate mortar and ground for 3~5 hours; The mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0017] In the step c, the pressure for briquetting is 15~18 kg / cm 2 , and the forming time is 0.8~1.5 min.

[0018] In the step c, the pressure of cold isostatic pressing is 300~350 MPa, and the holding time is 3~4 min.

[0019] In the step c, the third isostatic pressing block is sintered, the sintering temperature is 1250~1350°C, and the sintering time is 3~6h.

[0020] In the step d, the annealing temperature is 900~1200°C, and the annealing time is 30~60 min.

[0021] As mentioned above, the existing Ca-Ce-Nb-W-O-based ceramic materials with scheelite structure have a low melting point and a small high-temperature resistivity, resulting in a maximum upper temperature of only 700°C, which severely limits their application environment. Further, it is found that the existing Ca-Ce-Nb-W-O-based ceramic materials with scheelite structure are prone to generate CeNbO 4+δ superoxide at high temperatures, which will cause an excessive resistance drift rate and reduce its stability at high temperatures. How to effectively solve these problems has also become the focus of attention of researchers. Obviously, developing new NTC thermistor materials that maintain high-temperature stability in a wide temperature range has great market potential and application value. For this reason, this application provides a CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material and its preparation method, and its chemical composition is (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2)O4, where M is (Sm, Eu, La, Ho or Dy).

[0022] In a specific example, the specific steps of the aforementioned CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material are as follows.

[0023] (1) Weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M accurately according to the stoichiometric ratio. Among them, the oxide of M is samarium trioxide, europium trioxide, lanthanum trioxide, holmium trioxide or dysprosium trioxide.

[0024] (2) Put the components weighed in step (1) into a grinding machine, use agate balls as the grinding medium and ethanol as the dispersant to carry out ball milling to obtain a ball-milled slurry; after drying the obtained ball-milled slurry at 100 °C, place it in an agate mortar and grind for 1 to 3 hours to obtain a first powder.

[0025] (3) Put the first powder obtained in step (2) into a corundum crucible and calcine it at 1000 - 1100 °C for 3 - 5 hours, and then grind the calcined material to obtain a second powder. The specific grinding operation is as follows: Add a PVA solution (Chinese name of PVA: polyvinyl alcohol) as an organic binder to the calcined material, place it in an agate mortar and grind for 3 - 5 hours to obtain (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 powder; the mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0026] (4) Press the second powder obtained in step (3) into a block at a pressure of 15 - 18 kg / cm 2 , and the forming time is 0.8 - 1.5 minutes; then, perform cold isostatic pressing on it, keep it at a pressure of 300 - 350 MPa for 3 - 4 minutes to obtain a third isostatic pressed block; sinter the third isostatic pressed block at 1250 - 1350 °C for 3 - 6 hours, and the heating and cooling rate is 3 °C / min to obtain the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material.

[0027] (5) After coating the two sides of the prepared CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material with platinum paste electrodes, anneal it at 900 - 1200 °C for 30 minutes to obtain a thermistor with negative temperature coefficient characteristics in the temperature range of 200 °C - 1100 °C.

[0028] In summary, compared with the undoped CaCeNbWO8 material, the present application improves the configurational entropy through A-site doping, that is, the "3+2" combination method, successfully broadens the applicable temperature range, and has a negative temperature coefficient characteristic in the range of 200°C to 1100°C; the material constant is B 200℃ / 1100℃ = 6081 to 7210 ± 1.8% K, and shows good high-temperature aging stability at high temperatures (the resistance drift rate is less than 3.49 ± 0.03% after aging at 1000°C for 500 hours), further extending the use range of this material in the medium and high temperature regions.

[0029] Compared with the prior art, the improvement of the present invention lies in: (1) Compared with the existing scheelite-structured Ca-Ce-Nb-W-O-based ceramic materials, the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material of the present application has NTC characteristics in the temperature range of 200°C to 1100°C, and the working temperature range is greatly expanded; (2) The negative temperature coefficient thermosensitive ceramic material of the present application has a resistance drift rate of less than 3.49 ± 0.03% after aging at 1000°C for 500 hours, and has excellent high-temperature aging stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described by way of examples with reference to the accompanying drawings, wherein: Figure 1 is the XRD pattern of the negative temperature coefficient thermosensitive ceramic material of the present invention (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (M = Sm, Eu, La, Ho, Dy) and CaCeNbWO8.

[0031] Figure 2 is the resistivity-temperature curve pattern of the negative temperature coefficient thermosensitive ceramic material of the present invention (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (M = Sm, Eu, La, Ho, Dy) and CaCeNbWO8.

[0032] Figure 3 is the aging relationship pattern of the negative temperature coefficient thermosensitive ceramic material of the present invention (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (M = Sm, Eu, La, Ho, Dy) at 1000°C. Detailed implementation manners

[0033] All the features disclosed in this specification, or all the steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

[0034] Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically described, each feature is only an example in a series of equivalent or similar features.

[0035] Example 1 In this example, the preparation steps of the high-entropy ceramic negative temperature coefficient thermistor ceramic material (Ca 1 / 3 Ce 1 / 3 Sm 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (abbreviated as CCSNW) are as follows.

[0036] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, and samarium sesquioxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, use ethanol as the liquid-phase dispersant and agate balls as the grinding medium; after ball milling is completed, dry the wet-milled slurry at 100 °C; then put the dried powder into an agate mortar and manually grind it for 3 hours to obtain the first powder.

[0037] b. Put the first powder obtained in step a into a corundum crucible, calcine it at 1100 °C for 3 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: add a PVA solution as an organic binder to the calcined material, put it into an agate mortar and grind it for 3 hours to obtain the CCSNW powder; among them, the mass of the added PVA solution is 4 wt% of the mass of the calcined material.

[0038] c. Press the second powder obtained in step b into a block at a pressure of 15 kg / cm 2 for 0.8 minutes; then, perform cold isostatic pressing on it, keep it at a pressure of 300 MPa for 3 min to obtain the third isostatic pressed block; sinter the third isostatic pressed block at 1300 °C for 6 hours, and the heating and cooling rate is 3 °C / min to prepare the high-entropy negative temperature coefficient thermistor ceramic material CCSNW.

[0039] d. Coat platinum paste electrodes on both sides of the high-entropy negative temperature coefficient thermistor ceramic material CCSNW sintered in step c, anneal it at 1200 °C for 30 minutes, and cool it to room temperature to obtain the negative temperature coefficient thermistor.

[0040] It was measured that the negative temperature coefficient thermistor prepared in this example has a negative temperature coefficient characteristic in the temperature range of 200 °C to 1100 °C, and the material constant B 200℃ / 1100℃ = 6836.5 ± 0.49% K, ρ 1100℃ = 3.06×10 3 ± 1.07% Ω·cm, and the aging coefficient after aging for 500 hours at 1000 °C is 3.32 ± 0.02%.

[0041] Example 2 In this example, the preparation steps of the high-entropy ceramic negative temperature coefficient thermistor ceramic material (Ca 1 / 3 Ce 1 / 3 Eu 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (abbreviated as CCENW) are as follows.

[0042] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, and europium trioxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, ethanol is used as the liquid phase dispersant and agate balls are used as the grinding medium; after ball milling is completed, the wet-milled slurry is dried at 100 °C; then the dried powder is placed in an agate mortar and manually ground for 2 hours to obtain the first powder.

[0043] b. Place the first powder obtained in step a in a corundum crucible and calcine it at 1100 °C for 3 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: Add a PVA solution as an organic binder to the calcined material, place it in an agate mortar and grind it for 4 hours to obtain the CCENW powder; among them, the mass of the added PVA solution is 4 wt% of the mass of the calcined material.

[0044] c. Press the second powder obtained in step b into a block at a pressure of 16 kg / cm 2 for 1.0 minute; then, perform cold isostatic pressing on it, keep it at a pressure of 300 MPa for 3 min to obtain the third isostatic pressed block; sinter the third isostatic pressed block at 1300 °C for 6 hours, and the heating and cooling rate is 3 °C / min to prepare the high-entropy negative temperature coefficient thermistor ceramic material CCENW.

[0045] d. Coat platinum paste electrodes on both sides of the high-entropy negative temperature coefficient thermistor ceramic material CCENW sintered in step c, anneal it at 1200 °C for 30 minutes, and cool it to room temperature to obtain the negative temperature coefficient thermistor.

[0046] It was measured that the negative temperature coefficient thermistor prepared in this example has a negative temperature coefficient characteristic in the temperature range of 200°C to 1100°C, and the material constant B 200℃ / 1100℃ = 6553 ± 0.63% K, ρ 1100℃ = 2.89×10 3 ± 1.10% Ω·cm, and the aging coefficient after aging for 500 hours at 1000°C is 3.41 ± 0.03%.

[0047] Example 3 In this example, the preparation steps of the high-entropy ceramic negative temperature coefficient thermistor ceramic material (Ca 1 / 3 Ce 1 / 3 La 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (abbreviated as CCLNW) are as follows.

[0048] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, and lanthanum trioxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, ethanol is used as the liquid-phase dispersant and agate balls are used as the grinding medium; after ball milling is completed, the wet-milled slurry is dried at 100°C; then the dried powder is placed in an agate mortar and manually ground for 1 hour to obtain the first powder.

[0049] b. Place the first powder obtained in step a in a corundum crucible, calcine it at 1000°C for 5 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: Add PVA solution as an organic binder to the calcined material, place it in an agate mortar and grind it for 5 hours to obtain the CCLNW powder; among them, the mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0050] c. Press the second powder obtained in step b into a compact at a pressure of 18 kg / cm 2 for 1.5 minutes; then, perform cold isostatic pressing on it, keep it at a pressure of 350 MPa for 4 minutes to obtain the third isostatic pressed block; sinter the third isostatic pressed block at 1350°C for 3 hours, and the heating and cooling rate is 2°C / min to prepare the high-entropy negative temperature coefficient thermistor ceramic material CCLNW.

[0051] d. Coat platinum paste electrodes on both sides of the high-entropy negative temperature coefficient thermistor ceramic material CCLNW sintered in step c, anneal it at 900°C for 60 minutes, and cool it to room temperature to obtain the negative temperature coefficient thermistor.

[0052] It is measured that the negative temperature coefficient thermistor prepared in this embodiment has negative temperature coefficient characteristics in the temperature range of 200°C to 1100°C, and the material constant B 200℃ / 1100℃ = 7210 ± 1.8% K, ρ 1100℃ = 2.87×10 3 ± 1.37% Ω·cm, and the aging coefficient after aging for 500 hours at 1000°C is 3.49 ± 0.03%.

[0053] Example 4 In this embodiment, the preparation steps of the high-entropy ceramic negative temperature coefficient thermosensitive ceramic material (Ca 1 / 3 Ce 1 / 3 Ho 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (abbreviated as CCHNW) are as follows.

[0054] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, and holmium trioxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, use ethanol as the liquid-phase dispersant and agate balls as the grinding medium; after ball milling is completed, dry the wet-milled slurry at 100°C; then put the dried powder into an agate mortar and manually grind for 2 hours to obtain the first powder.

[0055] b. Put the first powder obtained in step a into a corundum crucible and calcine at 1100°C for 5 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: add a PVA solution as an organic binder to the calcined material, and grind it in an agate mortar for 3 hours to obtain the CCHNW powder; among them, the mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0056] c. Press the second powder obtained in step b into a block at a pressure of 17 kg / cm 2 for 1.5 minutes; then, perform cold isostatic pressing on it and keep it at a pressure of 350 MPa for 3 min to obtain the third isostatic pressing block; sinter the third isostatic pressing block at 1250°C for 6 hours, and the heating and cooling rate is 2°C / min to obtain the high-entropy negative temperature coefficient thermosensitive ceramic material CCHNW.

[0057] d. Coat platinum paste electrodes on both sides of the high-entropy negative temperature coefficient thermosensitive ceramic material CCHNW sintered in step c, anneal at 1100°C for 30 minutes, and cool to room temperature to obtain the negative temperature coefficient thermistor.

[0058] It is measured that the negative temperature coefficient thermistor prepared in this embodiment has a negative temperature coefficient characteristic in the temperature range of 200°C to 1100°C, and the material constant B 200℃ / 1100℃ = 6081 ± 0.22% K, ρ 1100℃ = 4.09×10 3 ± 1.02% Ω·cm, and the aging coefficient after aging for 500 hours at 1000°C is 2.71 ± 0.04%.

[0059] Example 5 In this embodiment, the preparation steps of the high-entropy ceramic negative temperature coefficient thermistor ceramic material (Ca 1 / 3 Ce 1 / 3 Dy 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4 (abbreviated as CCDNW) are as follows.

[0060] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide, and dysprosium trioxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, ethanol is used as the liquid-phase dispersant and agate balls are used as the grinding medium; after ball milling is completed, the wet-milled slurry is dried at 100°C; then the dried powder is placed in an agate mortar and manually ground for 1 hour to obtain the first powder.

[0061] b. Place the first powder obtained in step a in a corundum crucible and calcine it at 1000°C for 4 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: Add a PVA solution as an organic binder to the calcined material, place it in an agate mortar and grind it for 3 hours to obtain the CCDNW powder; among them, the mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0062] c. Press and form the second powder obtained in step b at a pressure of 18 kg / cm 2 for 1.0 minute; then, perform cold isostatic pressing on it and keep it at a pressure of 350 MPa for 3 min to obtain the third isostatic pressing block; sinter the third isostatic pressing block at 1300°C for 3 hours, and the heating and cooling rate is 2°C / min to prepare the high-entropy negative temperature coefficient thermistor ceramic material CCDNW.

[0063] d. Coat platinum paste electrodes on both sides of the high-entropy negative temperature coefficient thermistor ceramic material CCDNW sintered in step c, anneal it at 1200°C for 30 minutes, and cool it to room temperature to obtain the negative temperature coefficient thermistor.

[0064] It was measured that the negative temperature coefficient thermistor prepared in this example has a negative temperature coefficient characteristic in the temperature range of 200°C to 1100°C, and the material constant B 200℃ / 1100℃ = 6323 ± 0.02% K, ρ 1100℃ = 3.79×10 3 ± 1.09% Ω·cm, and the aging coefficient after aging for 500 hours at 1000°C is 3.44 ± 0.02%.

[0065] Comparative Example 1 In this example, the preparation steps of the negative temperature coefficient thermistor ceramic material CaCeNbWO8 (abbreviated as CCNW) are as follows.

[0066] a. According to the stoichiometric ratio, accurately weigh calcium carbonate, cerium dioxide, tungsten oxide, and niobium pentoxide, mix the weighed components, and then put the mixed powder into a ball mill for ball milling; when ball milling, use ethanol as the liquid phase dispersant and agate balls as the grinding medium; after ball milling is completed, dry the wet-milled slurry at 100°C; then put the dried powder into an agate mortar and manually grind it for 1 hour to obtain the first powder.

[0067] b. Put the first powder obtained in step a into a corundum crucible and calcine it at 1000°C for 3 hours, and then grind the calcined material to obtain the second powder. The specific grinding operation is as follows: add a PVA solution as an organic binder to the calcined material, and grind it in an agate mortar for 3 hours to obtain the CCNW powder; among them, the mass of the added PVA solution is 4wt% of the mass of the calcined material.

[0068] c. Press the second powder obtained in step b into a block at a pressure of 15 kg / cm 2 for 1.0 minute; then, perform cold isostatic pressing on it, keep it at a pressure of 300 MPa for 3 minutes to obtain the third isostatic pressing block; sinter the third isostatic pressing block at 1300°C for 3 hours, and the heating and cooling rate is 2°C / min to obtain the CaCeNbWO8 negative temperature coefficient thermistor ceramic material.

[0069] d. Coat platinum paste electrodes on both sides of the CaCeNbWO8 negative temperature coefficient thermistor ceramic material sintered in step c, anneal it at 900°C for 30 minutes, and cool it to room temperature to obtain the negative temperature coefficient thermistor.

[0070] It was measured that the negative temperature coefficient thermistor prepared in this example has a negative temperature coefficient characteristic in the temperature range of 25°C to 700°C, and the material constant B 25℃ / 700℃ = 5073 ± 1.23% K.

[0071] The upper and lower limit values and interval values of the process parameters (such as temperature, time, etc.) of the present invention can all implement this method, and the embodiments are not listed one by one here.

[0072] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be regarded as consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

[0073] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as to any new combination of the steps of any new method or process disclosed.

Claims

1. A CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material, characterized in that, Its chemical formula is (Ca 1 / 3 Ce 1 / 3M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4, where M is Sm, Eu, La, Ho or Dy.

2. The negative temperature coefficient thermosensitive ceramic material according to claim 1, wherein The electrical performance parameters of the negative temperature coefficient thermosensitive ceramic material are as follows: B 200℃ / 1100℃ = 6081 to 7210 ± 1.8% K, ρ 1100℃ = 2.87×10 3 ~ 4.09×10 3 ± 1.37% Ω·cm, and the applicable temperature range is 200°C to 1100°C.

3. The negative temperature coefficient thermosensitive ceramic material according to claim 1 or 2, characterized in that, The negative temperature coefficient thermosensitive ceramic material is prepared by mixing and firing raw materials calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M; M is Sm, Eu, La, Ho or Dy.

4. A method for preparing the negative temperature coefficient thermosensitive ceramic material according to any one of the preceding claims 1 to 3, characterized in that, It includes the following steps: a. According to the molar ratio of the chemical formula (Ca 1 / 3 Ce 1 / 3 M 1 / 3 )(Nb 1 / 2 W 1 / 2 )O4, weigh calcium carbonate, cerium dioxide, tungsten oxide, niobium pentoxide and the oxide of M respectively for mixing and ball milling, then dry and grind them to obtain the first powder; wherein the oxide of M is samarium trioxide, europium trioxide, lanthanum trioxide, holmium trioxide or dysprosium trioxide; b. Calcining and grinding the first powder obtained in step a to obtain a second powder; c. Compacting the second powder obtained in step b, and then performing cold isostatic pressing on the compacted block to obtain a third isostatic pressing block; sintering the third isostatic pressing block to obtain the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material.

5. The preparation method according to claim 4, characterized in that, It also includes the following steps: d. After coating platinum paste electrodes on both sides of the CaCeNbWO8-based high-entropy negative temperature coefficient thermosensitive ceramic material obtained in step c, annealing and then cooling to room temperature to obtain a thermistor with negative temperature coefficient characteristics in the temperature range of 200°C to 1100°C.

6. The preparation method according to claim 4 or 5, characterized in that, In the said step b, the calcining temperature is 1000 - 1100°C and the calcining time is 3 - 5h.

7. The preparation method according to claim 4, characterized in that, In the said step b, the grinding operation is as follows: adding a PVA solution as an organic binder to the calcined material, and grinding in an agate mortar for 3 - 5 hours; The mass of the added PVA solution is 4wt% of the mass of the calcined material.

8. The preparation method according to claim 4, characterized in that, In the step c, the pressure for forming the briquette is 15 - 18 kg / cm 2 , and the forming time is 0.8 - 1.5 min.

9. The preparation method according to any one of claims 4 to 8, characterized in that In the said step c, sintering the third isostatic pressing block, the sintering temperature is 1250 - 1350°C and the sintering time is 3 - 6h.

10. The preparation method according to any one of claims 4 to 9, characterized in that, In the said step d, the annealing temperature is 900 - 1200°C and the annealing time is 30 - 60min.

Images