High-entropy rare earth chromate negative temperature coefficient thermal sensitive ceramic material as well as preparation method and application thereof

Abstract

The invention discloses a high-entropy rare earth chromate negative temperature coefficient thermal sensitive ceramic material as well as a preparation method and application thereof, belongs to the field of high-temperature thermal sensitive sensors, and aims to solve the stability problem of chromium-based perovskite in high-temperature long-term use, especially the problem of electrical property reduction caused by Cr element volatilization. The thermal sensitive ceramic material with the negative temperature coefficient is prepared by the following steps: respectively mixing raw materials including lanthanum trioxide, neodymium oxide, samarium trioxide, europium oxide, gadolinium oxide and chromium sesquioxide with dysprosium oxide, holmium oxide, yttrium oxide and erbium oxide according to a stoichiometric ratio; and carrying out wet ball milling, drying, powder calcination, cold isostatic compaction and high-temperature sintering to obtain the perovskite structure (La1 / 6Nd1 / 6Sm1 / 6Eu1 / 6Gd1 / 6M1 / 6) CrO3 thermal sensitive ceramic material, and M is Dy, Ho, Y or Er. The electrical property parameters are as follows: B 25 DEG C / 1500 DEG C is equal to 1927-2011 K, rho 1500 DEG C is equal to 1.29 * 10 < 2 >-1.60 * 10 < 2 > omega.cm, and good high-temperature aging stability is shown at high temperature (the resistance drift rate after aging for 500 hours at 1500 DEG C is less than 4.6%).

Description

Technical Field

[0001] The present application relates to the field of high-temperature thermistors, and in particular to a high-entropy rare earth chromate negative temperature coefficient thermistor ceramic material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, national industrial adjustments and technological upgrades have driven the demand for miniaturization and economy of temperature sensors in various fields. Compared with expensive precious metal thermocouples, negative temperature coefficient (NTC) thermistors have received widespread attention in applications such as temperature detection and circuit protection, and the corresponding demand is also increasing. At the same time, with the continuous advancement of technology in aerospace, national defense science and technology and other fields, the requirements for high-temperature performance of equipment are also increasing. This requires NTC thermistors to maintain excellent high-temperature aging stability while meeting a higher applicable temperature limit.

[0003] At present, common NTC materials (such as spinel oxides) have poor phase stability and sensitivity at high temperatures above 300°C, which limits their application range. At present, the research focus of NTC materials has shifted to chromium-based perovskites and their composite materials. Chromium-based perovskite ceramics are suitable for a wide temperature range (25°C~900°C) and have adjustable electrical properties, but at high temperatures, element volatilization is prone to occur, which makes it difficult for the material to form a dense microstructure during the sintering process and causes continuous changes in resistance values, thereby affecting high-temperature reliability and production feasibility. Although composite ceramics of high-resistance phase oxides and low-resistance phase perovskites can theoretically be used for high-temperature NTC materials, the two-phase percolation problem in practical applications causes large resistance drift at high temperatures.

[0004] Therefore, there is an urgent need to develop new NTC materials to meet the increasingly stringent high-temperature performance standards. Summary of the invention

[0005] The invention of this application aims to provide a high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, its preparation method and application, so as to solve the stability problem of chromium-based perovskite and its composite thermistor ceramic in high temperature and long-term use, especially the problem of electrical performance degradation caused by Cr volatilization. The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material of this application has an ultra-wide temperature range of 25~1500℃ and exhibits excellent aging stability at an upper temperature of 1500℃.

[0006] In order to achieve the above purpose, this application adopts the following technical solutions: A high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, the chemical formula of which is (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 M1 / 6 )CrO3, wherein M is Dy, Ho, Y or Er.

[0007] The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material has a negative temperature coefficient characteristic in the range of 25°C to 1500°C.

[0008] The applicable temperature range of the high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is 25°C to 1500°C.

[0009] The electrical performance parameters of the high entropy rare earth chromate negative temperature coefficient thermistor ceramic material are as follows: 25℃ / 1500℃ =1927~2011 K,ρ 1500℃ =1.29×10 2 ~1.60×10 2 Ω·cm.

[0010] The resistance drift rate of the high-entropy rare earth chromate negative temperature coefficient thermistor ceramic material is less than 4.6% after aging at 1500°C for 500 hours.

[0011] The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is prepared by mixing and sintering raw materials of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, oxide of M and chromium trioxide according to a chemical formula molar ratio; the oxide of M is dysprosium trioxide, holmium trioxide, yttrium trioxide or erbium trioxide.

[0012] The preparation method of the above-mentioned high-entropy rare earth chromate negative temperature coefficient thermistor ceramic material is prepared by mixing and sintering the raw materials of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, chromium trioxide and M oxide according to the chemical formula molar ratio; the oxide of M is dysprosium trioxide, holmium trioxide, yttrium trioxide or erbium trioxide.

[0013] The steps include: a. According to the molar ratio of La:Nd:Sm:Eu:Gd M:Cr=1:1:1:1:1:1:6, lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, oxide of M and chromium trioxide are weighed and mixed to obtain an initial mixture; the initial mixture is ground to obtain a precursor powder; wherein M is Dy, Ho, Y or Er, and the oxide of M is dysprosium trioxide, holmium trioxide, yttrium trioxide or erbium trioxide; b. calcining the precursor powder obtained in step a, and then grinding it to obtain chromate powder; c. Dry-pressing the chromate powder obtained in step b to obtain a dry-pressed block; cold isostatically pressing the dry-pressed block to obtain a cold isostatically pressed block; and sintering the cold isostatically pressed block to obtain a high-entropy rare earth chromate negative temperature coefficient thermistor ceramic material.

[0014] In the step a, the process of grinding the initial mixture is as follows: the initial mixture is wet ball-milled, then dried, and then ground to obtain a precursor powder.

[0015] In the step a, the liquid phase dispersant of wet ball milling is deionized water, and the grinding medium is agate balls.

[0016] In the step a, the process of grinding the initial mixture is as follows: wet ball milling the initial mixture, drying the slurry after wet ball milling, taking out the dried material and grinding it to obtain a precursor powder.

[0017] In the step a, the initial mixture is wet-milled by liquid-assisted three-dimensional vibration ball milling for 8 to 10 hours; the drying temperature is 80 to 120° C.; the dried material is taken out and placed in an agate mortar for manual grinding for 1 to 3 hours.

[0018] In the step b, the calcination temperature is 900° C. to 1300° C., and the calcination time is 2 to 5 hours; after calcination, the chromate powder is ground into powder to obtain chromate powder.

[0019] In the step b, the precursor powder obtained in the step a is placed in a corundum crucible for calcination.

[0020] In the step b, after calcination, the chromate powder (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 M 1 / 6 )CrO3, wherein M is Dy, Ho, Y or Er.

[0021] In step c, the pressure of dry pressing is 15-18 kg / cm 2 .

[0022] In the step c, the chromate powder obtained in the step b is pressed by a uniaxial hydraulic press at 15-18 kg / cm 2 The dry pressing is performed under a pressure of to obtain a dry pressed block.

[0023] In the step c, the dry pressing time is 0.5 to 10 minutes.

[0024] In the step c, the dry pressed block is subjected to cold isostatic pressing at a pressure of 270-300 MPa to obtain a cold isostatic pressed block.

[0025] In the step c, the holding time of the cold isostatic pressing is 3 to 20 minutes.

[0026] In the step c, the dry pressed block is subjected to cold isostatic pressing, and the pressure is maintained at 270-300 MPa for 3-20 minutes to obtain a cold isostatic pressed block.

[0027] In the step c, the sintering temperature is 1500° C. to 1600° C., and the sintering time is 10 to 12 hours.

[0028] An application of a high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, the chemical formula of which is (La 1 / 6 Nd 1 / 6Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3, wherein M is Dy, Ho, Y or Er.

[0029] The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is used to prepare high temperature thermistor.

[0030] The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is used to prepare a negative temperature coefficient thermistor.

[0031] As mentioned above, in order to improve the stability and reliability of chromium-based perovskite and its composite thermistor ceramics in high temperature environments, the present invention proposes a new type of high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, its preparation method and application. The chemical formula of the rare earth chromate negative temperature coefficient thermistor ceramic material is (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3 (M = Dy, Ho, Y or Er), this material system has negative temperature coefficient characteristics within 25℃~1500℃, and is a high-entropy rare earth chromate high-temperature negative temperature coefficient thermistor ceramic material, that is, a new type of high-temperature thermistor ceramic with an ultra-wide working temperature range of 25℃~1500℃ and excellent aging stability. This series of negative temperature coefficient thermistor materials are made of raw materials chromium trioxide, lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, chromium trioxide and M oxides mixed and fired according to the chemical formula molar ratio (M oxides are dysprosium trioxide, holmium trioxide, yttrium trioxide and erbium trioxide).

[0032] The inventors have found that high entropy rare earth chromate (La1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3 (M = Dy, Ho, Y or Er) has obvious negative temperature coefficient characteristics in the temperature range of 25℃~1500℃. This type of high entropy material shows an ultra-wide test temperature range, and the maximum temperature limit can reach 1500℃; at the same time, due to its entropy-stabilized structure, it shows excellent high-temperature aging stability. The relationship between the resistance drift rate and the aging time of the prepared ceramic material at 1500℃ was measured. The test results show that the resistance drift rate is less than 4.6% after aging for 500 hours, and it can be used to manufacture long-life high-temperature negative temperature coefficient thermistors. The high-entropy rare earth chromate of this application forms a high entropy effect through the synergistic effect of multiple main elements, which thermodynamically improves the stability of high-temperature phases and structures; severe lattice distortion reduces thermal conductivity and material constant B value, thereby expanding the application temperature range. At the same time, the hysteresis diffusion effect of high-entropy ceramics brings excellent antioxidant properties, making it suitable for different oxygen atmospheres. The material has stable high-temperature electrical properties and high linear correlation, and is suitable for manufacturing thermistor devices in high-temperature environments.

[0033] In summary, the present application provides a series of novel high-entropy rare earth chromate negative temperature coefficient thermistor ceramic materials with an ultra-wide operating temperature range of 25°C to 1500°C and excellent aging stability, as well as preparation methods and applications thereof in the field of semiconductor sensors. The high-entropy rare earth chromate negative temperature coefficient thermistor ceramic materials of the present application are prepared by mixing raw materials of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, oxide of M and chromium trioxide in a stoichiometric ratio, and then wet ball milling, drying, powder calcination, dry pressing, cold isostatic pressing, and high-temperature sintering to obtain a perovskite structure (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3 thermistor ceramic material, where M is Dy, Ho, Y or Er. Its electrical performance parameters are: B 25℃ / 1500℃ =1927~2011 K,ρ 1500℃ =1.29×10 2 ~1.60×10 2 Ω·cm, and shows good high temperature aging stability at high temperature (the resistance drift rate is less than 4.6% after aging for 500 hours at 1500°C). It can be seen that the high entropy rare earth chromate of the present invention is a high temperature negative temperature coefficient thermistor ceramic material with a high upper limit of working temperature, an ultra-wide applicable temperature range and excellent aging stability.

[0034] Due to the adoption of the above technical solution, the beneficial effects of the present invention are: (1) Thermosensitive material of the present invention (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3 (M = Dy, Ho, Y or Er) has NTC characteristics in the temperature range of 25℃~1500℃, with a wide test temperature range and a high upper limit of operating temperature; (2) Thermosensitive material of the present invention (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3 (M = Dy, Ho, Y or Er) aged at 1500℃ for 500 hours, the resistance drift rate is less than 4.6%, showing excellent high temperature aging stability; (3) Thermosensitive material of the present invention (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3(M= Dy, Ho, Y or Er) has a higher resistivity in high temperature environment, which ensures the accuracy of its measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 )The relationship between the resistivity and temperature of CrO3 ceramic material.

[0036] Figure 2 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Ho 1 / 6 )The relationship between the resistivity and temperature of CrO3 ceramic material.

[0037] Figure 3 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y1 / 6 )The relationship between the resistivity and temperature of CrO3 ceramic material.

[0038] Figure 4 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Er 1 / 6 )The relationship between the resistivity and temperature of CrO3 ceramic material.

[0039] Figure 5 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 ) Relationship between resistance drift rate and aging time of CrO3 ceramic material at 1500℃.

[0040] Figure 6 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Ho 1 / 6 ) Relationship between resistance drift rate and aging time of CrO3 ceramic material at 1500℃.

[0041] Figure 7 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y 1 / 6 )Relationship between resistance drift rate and aging time of CrO3 ceramic material at 1500℃.

[0042] Figure 8 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Er 1 / 6 )Relationship between resistance drift rate and aging time of CrO3 ceramic material at 1500℃.

[0043] Fig. 9 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 )CrO3、(La 1 / 6 Nd 1 / 6 Sm1 / 6 Eu 1 / 6 G 1 / 6 Ho 1 / 6 )CrO3、(La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y 1 / 6 )CrO3、(La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Er 1 / 6 )Summary of the relationship between resistivity and temperature of CrO3 ceramic materials. DETAILED DESCRIPTION

[0044] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0045] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0046] Example 1 In this embodiment, the high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6E 1 / 6 G 1 / 6 Dy 1 / 6 )The preparation process of CrO3 is as follows.

[0047] a. According to the molar ratio of La:Nd:Sm:Eu:Gd:Dy:Cr=1:1:1:1:1:1:6, weigh the oxide powders of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, dysprosium trioxide and chromium trioxide respectively and mix them to obtain an initial mixture. Place the initial mixture in a ball mill, use agate as the ball milling medium, and use deionized water as the dispersion medium. After liquid-assisted three-dimensional vibration wet ball milling for 8 hours, dry the wet-milled slurry at a temperature of 80°C; then take it out, place it in an agate mortar, and grind it manually for 1 hour to obtain a precursor powder.

[0048] b. The precursor powder obtained in step a was calcined at 900° C. for 2 hours and then manually ground for 1 hour to obtain chromate powder.

[0049] c. The chromate powder obtained in step b was pressurized by a uniaxial hydraulic press at 15 kg / cm 2 The dry pressed block was subjected to cold isostatic pressing at a pressure of 270 MPa for 3 minutes to obtain a cold isostatic pressed block. The cold isostatic pressed block was sintered at a temperature of 1500°C for 10 hours to obtain a high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 )CrO3.

[0050] The obtained high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 Dy 1 / 6 )CrO3 is tested for electrical properties. The relationship between resistivity and temperature is as follows Figure 1 As shown, the electrical parameters of the material are B 25℃ / 1500℃ =1927 K,ρ 1500℃ =1.29×10 2 Ω·cm. At the same time, the prepared (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 ) The relationship between the resistance drift rate and aging time of CrO3 ceramic material at 1500℃ was measured. The test results are as follows Figure 5 shown.

[0051] Example 2 In this embodiment, the high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6E 1 / 6 G 1 / 6 Ho 1 / 6 )The preparation process of CrO3 is as follows.

[0052] a. According to the molar ratio of La:Nd:Sm:Eu:Gd:Ho:Cr=1:1:1:1:1:1:6, weigh the oxide powders of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, holmium trioxide and chromium trioxide respectively and mix them to obtain an initial mixture. Place the initial mixture in a ball mill, use agate as the ball milling medium, and use deionized water as the dispersion medium. After liquid-assisted three-dimensional vibration wet ball milling for 8.5 hours, dry the wet-milled slurry at a temperature of 95°C; then take it out, place it in an agate mortar, and grind it manually for 1.5 hours to obtain a precursor powder.

[0053] b. The precursor powder obtained in step a was calcined at 1100° C. for 3 hours and then manually ground for 2 hours to obtain chromate powder.

[0054] c. The chromate powder obtained in step b was pressurized by a uniaxial hydraulic press at 16 kg / cm 2 The dry pressed block was subjected to cold isostatic pressing at a pressure of 280 MPa for 10 minutes to obtain a cold isostatic pressed block. The cold isostatic pressed block was sintered at a temperature of 1550°C for 10.5 hours to obtain a high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Ho 1 / 6 )CrO3.

[0055] The obtained high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 Ho 1 / 6 )CrO3 is tested for electrical properties. The relationship between resistivity and temperature is as follows Figure 2 As shown, the electrical parameters of the material are B 25℃ / 1500℃ =1950 K, ρ 1500℃ =1.44×10 2 Ω·cm. At the same time, the prepared (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Ho 1 / 6 ) The relationship between the resistance drift rate and aging time of CrO3 ceramic material at 1500 ℃ was measured. The test results are as follows Figure 6 shown.

[0056] Example 3 In this embodiment, the high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6E 1 / 6 G 1 / 6 Y 1 / 6 )The preparation process of CrO3 is as follows.

[0057] a. According to the molar ratio of La:Nd:Sm:Eu:Gd:Y:Cr=1:1:1:1:1:1:6, weigh the oxide powders of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, yttrium trioxide and chromium trioxide respectively and mix them to obtain an initial mixture. Place the initial mixture in a ball mill, use agate as the ball milling medium, and use deionized water as the dispersion medium. After liquid-assisted three-dimensional vibration wet ball milling for 9 hours, dry the wet-milled slurry at a temperature of 100°C; then take it out, place it in an agate mortar, and grind it manually for 1.5 hours to obtain a precursor powder.

[0058] b. The precursor powder obtained in step a was calcined at 1200° C. for 4 hours and then manually ground for 4 hours to obtain chromate powder.

[0059] c. The chromate powder obtained in step b was pressurized by a uniaxial hydraulic press at 17 kg / cm 2 The dry pressed block was subjected to cold isostatic pressing at a pressure of 290 MPa for 15 minutes to obtain a cold isostatic pressed block. The cold isostatic pressed block was sintered at a temperature of 1580°C for 11 hours to obtain a high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y 1 / 6 )CrO3.

[0060] The obtained high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 Y 1 / 6 )CrO3 is tested for electrical properties. The relationship between resistivity and temperature is as follows Figure 3 As shown, the electrical parameters of the material are B 25℃ / 1500℃ =1969 K,ρ 1500℃ =1.51×10 2 Ω·cm. At the same time, the prepared (La 1 / 6Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y 1 / 6 ) The relationship between the resistance drift rate and aging time of CrO3 ceramic material at 1500℃ was measured. The test results are as follows Figure 7 shown.

[0061] Example 4 In this embodiment, the high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6E 1 / 6 G 1 / 6 Er 1 / 6 )The preparation process of CrO3 is as follows.

[0062] a. According to the molar ratio of La:Nd:Sm:Eu:Gd:Er:Cr=1:1:1:1:1:1:6, weigh the oxide powders of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, erbium trioxide and chromium trioxide respectively and mix them to obtain an initial mixture. Place the initial mixture in a ball mill, use agate as the ball milling medium, and use deionized water as the dispersion medium. After liquid-assisted three-dimensional vibration wet ball milling for 10 hours, dry the wet-milled slurry at a temperature of 120°C; then take it out, place it in an agate mortar, and grind it manually for 3 hours to obtain a precursor powder.

[0063] b. The precursor powder obtained in step a was calcined at 1300° C. for 5 hours and then manually ground for 5 hours to obtain chromate powder.

[0064] c. The chromate powder obtained in step b was pressurized by a uniaxial hydraulic press at 18 kg / cm 2 The dry pressed block was subjected to cold isostatic pressing at a pressure of 300 MPa for 20 minutes to obtain a cold isostatic pressed block. The cold isostatic pressed block was sintered at a temperature of 1600°C for 12 hours to obtain a high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Er 1 / 6 )CrO3.

[0065] The obtained high entropy rare earth chromate high temperature negative temperature coefficient thermistor ceramic material (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6Gd 1 / 6 Er 1 / 6 )CrO3 is tested for electrical properties. The relationship between resistivity and temperature is as follows Figure 4 As shown, the electrical parameters of the material are B 25℃ / 1500℃ =2011 K,ρ 1500℃ =1.60×10 2 Ω·cm. At the same time, the prepared (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Er 1 / 6 ) The relationship between the resistance drift rate and aging time of CrO3 ceramic material at 1500 ℃ was measured. The test results are as follows Figure 8 shown.

[0066] Fig. 9 for (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Dy 1 / 6 )CrO3 ceramic materials, (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6Ho 1 / 6 )CrO3 ceramic materials, (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 Y 1 / 6 )CrO3 ceramic materials, (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6E 1 / 6 )Summary of the relationship between resistivity and temperature of CrO3 ceramic materials.

[0067] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

[0068] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements and corrections to this specification. Such modifications, improvements and corrections are suggested in this specification, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this specification.

[0069] At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined.

[0070] In addition, unless explicitly stated in the claims, the order of the processing elements and sequences described in this specification, the use of alphanumeric characters, or the use of other names are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some invention embodiments that are currently considered useful through various examples, it should be understood that such details are only for illustrative purposes, and the attached claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the essence and scope of the embodiments of this specification.

[0071] Similarly, it should be noted that in order to simplify the description disclosed in this specification and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this specification, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the subject matter of this specification are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0072] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this specification is hereby incorporated by reference in its entirety. Except for application history documents that are inconsistent with or conflicting with the contents of this specification, documents that limit the broadest scope of the claims of this specification (currently or later attached to this specification) are also excluded. It should be noted that if the descriptions, definitions, and / or use of terms in the materials attached to this specification are inconsistent or conflicting with the contents described in this specification, the descriptions, definitions, and / or use of terms in this specification shall prevail.

[0073] 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, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered 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.

Claims

1. A high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, characterized in that: Its chemical formula is (La 1 / 6 Nd 1 / 6Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3, wherein M is Dy, Ho, Y or Er.

2. The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material according to claim 1, characterized in that: The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material has a negative temperature coefficient characteristic in the range of 25-1500°C.

3. The method for preparing the high entropy rare earth chromate negative temperature coefficient thermistor ceramic material according to claim 1 or 2, characterized in that: The raw materials of lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, chromium trioxide and oxide of M are mixed and fired according to the chemical formula molar ratio; in the oxide of M, M is Dy, Ho, Y or Er.

4. The preparation method according to claim 3, characterized in that: The steps include: a. According to the molar ratio of La:Nd:Sm:Eu:Gd M:Cr=1:1:1:1:1:1:6, lanthanum trioxide, neodymium trioxide, samarium trioxide, europium trioxide, gadolinium trioxide, oxide of M and chromium trioxide are weighed and mixed to obtain an initial mixture; the initial mixture is ground to obtain a precursor powder; wherein M is Dy, Ho, Y or Er, and the oxide of M is dysprosium trioxide, holmium trioxide, yttrium trioxide or erbium trioxide; b. calcining the precursor powder obtained in step a, and then grinding it to obtain chromate powder; c. Dry-pressing the chromate powder obtained in step b to obtain a dry-pressed block; cold isostatically pressing the dry-pressed block to obtain a cold isostatically pressed block; and sintering the cold isostatically pressed block to obtain a high-entropy rare earth chromate negative temperature coefficient thermistor ceramic material.

5. The preparation method according to claim 4, characterized in that: In the step a, the process of grinding the initial mixture is as follows: the initial mixture is wet ball-milled, then dried, and then ground to obtain a precursor powder.

6. The preparation method according to claim 4 or 5, characterized in that: In the step b, the calcination temperature is 900° C. to 1300° C., and the calcination time is 2 to 5 hours; after calcination, the chromate powder is ground into powder to obtain chromate powder.

7. The preparation method according to any one of claims 4 to 6, characterized in that In the step c, the sintering temperature is 1500-1600° C. and the sintering time is 10-12 hours.

8. An application of a high entropy rare earth chromate negative temperature coefficient thermistor ceramic material, characterized in that: Its chemical formula is (La 1 / 6 Nd 1 / 6 Sm 1 / 6 Eu 1 / 6 G 1 / 6 M 1 / 6 )CrO3, wherein M is Dy, Ho, Y or Er.

9. The use according to claim 8, characterized in that: The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is used to prepare high temperature thermistor.

10. The use according to claim 8, characterized in that: The high entropy rare earth chromate negative temperature coefficient thermistor ceramic material is used to prepare a negative temperature coefficient thermistor.

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