Perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic and preparation method thereof

Abstract

This invention discloses a perovskite-structured high-entropy negative temperature coefficient thermistor ceramic and its preparation method. The high-entropy negative temperature coefficient thermistor ceramic is prepared by sintering a mixture of oxides of lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, and RE, along with manganese dioxide. The oxides of RE are yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide, or scandium trioxide. The material constant B of the high-entropy negative temperature coefficient thermistor ceramic is... ‑75 / 150℃ =1960K~2654K, resistivity ρ 0℃ =2122Ω·cm~6807Ω·cm, applicable temperature range is -75℃~150℃.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy ceramics, and particularly relates to a perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic and a preparation method thereof. BACKGROUND

[0002] High-entropy ceramics are inorganic compounds A m B n X y One or more Wyckoff sites are occupied by equal atomic ratio or close to equal atomic ratio, usually 5 or more multi-components to form a solid solution, which has high-entropy effect, lattice distortion effect, delayed diffusion effect and cocktail effect in performance.

[0003] The perovskite type composite oxide is a new type of inorganic non-metallic material with unique physical and chemical properties. The perovskite structure of LaMnO3 is a cubic cell, and the chemical formula is AB03, wherein, for example, La 3+ Ions occupy eight vertices of the cube, and Mn 3+ Ions are located at the center of the cube, and O ions are located at the face center of the cube. The perovskite structure of LaMnO3 has good electrical conductivity and low resistance at room temperature. However, it cannot be used alone as a thermosensitive ceramic because of its small resistance. SUMMARY

[0004] In view of the above problems, the main purpose of the present application is to provide a perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic and a preparation method thereof.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows:

[0006] As a first aspect of the present application, a perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic is provided, and the chemical formula is (La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 RE 0.2 )MnO3, wherein RE is one of Y, Ce, Dy, Ho, Yb and Sc.

[0007] Further, the material constant B -75 / 150℃ of the high-entropy negative temperature coefficient thermosensitive ceramic is 1960K-2654K, the resistivity p 0℃ =2122Ω·cm-6807Ω·cm, and the applicable temperature range is-75℃-150℃.

[0008] Further, the high-entropy negative temperature coefficient thermosensitive ceramic is prepared by mixing and sintering lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, RE oxide and manganese dioxide, wherein the RE oxide is yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide or scandium trioxide.

[0009] Further, the high-entropy negative temperature coefficient thermosensitive ceramic has an electrical resistance drift rate of less than 1% after being aged for 500 hours at 125 ℃.

[0010] As a second aspect of the present application, a preparation method of a high-entropy negative temperature coefficient thermosensitive ceramic with a high-entropy perovskite structure is provided, comprising:

[0011] The lanthanum trioxide, the neodymium trioxide, the samarium trioxide, the gadolinium trioxide, the RE oxide and the manganese dioxide are mixed and then sequentially subjected to wet grinding, drying and grinding treatment to obtain a precursor powder; wherein the RE oxide is yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide or scandium trioxide.

[0012] The precursor powder is calcined and ground into a powder to obtain a perovskite phase powder.

[0013] The perovskite phase powder is sequentially subjected to compression molding and sintering treatment to obtain the high-entropy negative temperature coefficient thermosensitive ceramic with a high-entropy perovskite structure.

[0014] Further, the molar ratio of La:Nd:Sm:Gd:RE:Mn in the high-entropy negative temperature coefficient thermosensitive ceramic is 1:1:1:1:1:5.

[0015] Further, the compression molding of the perovskite phase powder comprises:

[0016] The molded block of the perovskite phase powder is subjected to cold isostatic pressing treatment to obtain a static pressing block.

[0017] Further, the calcination temperature is 1000-1200 ℃, and the calcination time is 2-4 h.

[0018] Further, the cold isostatic pressing pressure is 300-350 MPa, and the pressure holding time is 180-240 s.

[0019] Further, the sintering temperature is 1200-1350 ℃, and the sintering time is 12-24 h.

[0020] According to the embodiment of the present application, by doping a high-entropy ceramic structure composed of La, Nd, Sm, Gd and RE on a LaMnO3 perovskite structure, the electrons are distributed in the Mn 3+ / Mn 4+The high-entropy oxide structure formed by doping in the perovskite structure of LaMnO3 greatly reduces the symmetry, greatly increases the octahedral distortion degree, and correspondingly reduces the overlap and interaction. The hysteresis diffusion effect of the high-entropy ceramic slows down the migration rate of the cations and reduces the resistance drift rate, thereby improving the aging stability of the thermistor. To some extent, the limitations of using LaMnO3 perovskite ceramic for negative temperature coefficient thermistor ceramic are overcome, and a new type of perovskite structure high-entropy negative temperature coefficient thermistor ceramic is provided. The selectivity of negative temperature coefficient thermistor materials in production and application is also expanded. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 X-ray diffraction patterns of high-entropy ceramics prepared according to embodiments 1-5 of the present application.

[0023] Figure 2 Temperature-resistance characteristic curves of high-entropy ceramics prepared according to embodiments 1-5 of the present application.

[0024] Figure 3 Resistance drift rate curves of high-entropy ceramics prepared according to embodiments 1-5 of the present application at 125℃.

[0025] Figure 4 Temperature-resistance characteristic curves of LaMnO3 in the present application comparative example 1.

[0026] Figure 5 Resistance drift curves of LaMnO3 thermistor at 125℃ in the present application comparative example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will be further described in detail with reference to the specific embodiments and the accompanying drawings.

[0028] The resistivity of negative temperature coefficient thermistor ceramic (NTC) decreases exponentially with temperature rise, and is mainly used for temperature measurement and temperature compensation. The resistance of LaMnO3 perovskite structure is small, and it cannot be used alone as a thermistor material. The lattice distortion effect and hysteresis diffusion effect possessed by high-entropy ceramics can increase the resistivity of the material and improve the aging stability.

[0029] Based on this, according to the embodiment of the present application, a perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic is provided, and the chemical formula of the high-entropy negative temperature coefficient thermosensitive ceramic is (La 0.2 Nd 0.2 Sm 0.2 Gd 0.2 RE 0.2 )MnO3, wherein RE is one of Y, Ce, Dy, Ho, Yb and Sc.

[0030] According to the embodiment of the present application, by doping on the LaMnO3 perovskite structure to form a high-entropy ceramic structure composed of La, Nd, Sm, Gd and RE, the symmetry of the structure is greatly reduced, the octahedral distortion degree is greatly increased, and the overlap and interaction are also reduced accordingly, thereby causing the resistivity to increase; secondly, the hysteresis diffusion effect of the high-entropy ceramic can slow down the migration rate of the cations, thereby reducing the resistance drift rate and improving the aging stability of the thermistor. The present application overcomes the limitations of LaMnO3 perovskite ceramic for negative temperature coefficient thermosensitive ceramic, provides a new type of perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic, and also expands the selectivity of negative temperature coefficient thermistor materials in production and application.

[0031] According to the embodiment of the present application, the material constant B -75 / 150℃ of the high-entropy negative temperature coefficient thermosensitive ceramic is 1960K-2654K, the resistivity p 0℃ is 2122Ω·cm-6807Ω·cm, and the applicable temperature range is -75℃-150℃.

[0032] According to the embodiment of the present application, the high-entropy negative temperature coefficient thermosensitive ceramic is mixed and fired by lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, RE oxide and manganese dioxide, wherein the RE oxide is yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide or scandium trioxide.

[0033] According to the embodiment of the present application, the high-entropy negative temperature coefficient thermosensitive ceramic has a resistance drift rate of less than 1% after aging for 500 hours at 125℃.

[0034] According to the embodiment of the present application, a preparation method of a high-entropy negative temperature coefficient thermosensitive ceramic is provided, comprising steps S101-S103:

[0035] In step S101, after the lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, RE oxide and manganese dioxide are mixed, wet grinding, drying and grinding treatment are sequentially performed to obtain a precursor powder;

[0036] In step S102, the precursor powder is calcined and ground into a powder to obtain a perovskite phase powder;

[0037] In step S103, the perovskite phase powder is sequentially subjected to compression molding and sintering treatment, to obtain a high-entropy negative temperature coefficient thermosensitive ceramic.

[0038] The oxide of RE is yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide or scandium trioxide.

[0039] According to the embodiment of the present application, by doping the high-entropy ceramic structure composed of La, Nd, Sm, Gd and RE on the LaMnO3 perovskite structure, the symmetry of the high-entropy oxide structure formed by doping in the LaMnO3 perovskite structure is greatly reduced, the octahedral distortion degree is greatly increased, and the overlap and interaction are also reduced accordingly. The high-entropy ceramic hysteresis diffusion effect slows down the migration rate of cations, reduces the resistance drift rate, and thus improves the aging stability of the thermistor. To some extent, the limitation of using LaMnO3 perovskite ceramic for negative temperature coefficient thermosensitive ceramic is overcome, and a new type of perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic is provided. The selectivity of negative temperature coefficient thermistor material in production and application is also expanded.

[0040] According to the embodiment of the present application, in step S101, oxide powders lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, the oxide of RE and manganese dioxide are weighed according to the molar ratio of La:Nd:Sm:Gd:RE:Mn=1:1:1:1:1:5, mixed to obtain a mixture; the mixture is placed in a ball mill jar, zirconium dioxide balls are used as the ball milling medium, and analytical pure anhydrous ethanol and deionized water are used as the dispersion medium. The wet ball milling is carried out at 200r / min-300r / min for 8-12 hours, the slurry after ball milling is dried at 60-100℃, and then taken out and ground in an agate mortar for 1-4 hours to obtain a precursor powder.

[0041] Preferably, the oxide of RE can be yttrium trioxide, cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide or scandium trioxide. Preferably, the wet ball milling time can be 8 hours, 10 hours, 12 hours, etc.; the wet ball milling speed can be 200r / min, 220r / min, 240r / min, 280r / min, 300r / min, etc.; the drying temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, etc.; and the grinding time can be 1 hour, 1.5 hours, 3 hours, 4 hours, etc.

[0042] According to the embodiment of the present application, in step S102, the obtained precursor powder is calcined at 1000-1200℃ for 2-4 hours, taken out and ground in an agate mortar for 1-4 hours to obtain the perovskite phase powder. Preferably, the calcination temperature can be 1000℃, 1100℃, 1200℃, etc., and the grinding time can be 1 hour, 1.5 hours, 3 hours, 4 hours, etc.

[0043] According to the embodiment of the present application, in order to obtain a ceramic material with high density subsequently, the press forming in step 103 can include: performing cold isostatic pressing treatment on the formed block after the perovskite phase powder is briquetted to form a block, to obtain a static pressure block.

[0044] According to the embodiment of the present application, further, in step S103, a certain amount of perovskite phase powder is weighed and poured into a mold with a diameter of 10 mm, for example, and a hydraulic press can be used with a pressure of 20-40 megapascals, and the pressure holding time can be 50-70 seconds, for example, to press the perovskite phase powder into a perovskite phase formed block; the perovskite phase formed block is placed in a cold isostatic press for cold isostatic pressing, and the cold isostatic pressing pressure can be 300-350 megapascals, for example, and the pressure holding time can be 180-240 seconds, for example, to obtain a static pressure block; the perovskite phase static pressure block is sintered at a temperature of 1200-1350℃ for 12-24 hours to obtain a perovskite structure negative temperature coefficient thermosensitive ceramic.

[0045] Preferably, the pressure of briquetting forming can be 20 megapascals, 30 megapascals, 40 megapascals, etc., and the pressure holding time of briquetting forming is 50-70 seconds; the cold isostatic pressing pressure can be 300 megapascals, 310 megapascals, 320 megapascals, 330 megapascals, 340 megapascals, 350 megapascals, etc., and the pressure holding time is 180 seconds, 200 seconds, 220 seconds, 240 seconds, etc.; the sintering temperature can be 1200℃, 1250℃, 1300℃, 1350℃, etc., and the sintering time can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0046] The high-entropy negative temperature coefficient thermosensitive ceramic prepared according to the embodiment of the present application is formed by doping high-entropy ceramic in lanthanum manganate, which further improves the resistivity of the lanthanum manganate thermosensitive material. As shown in FIG. 6, the resistance-temperature characteristic curve shows that the high-entropy ceramic has obvious NTC characteristics. As shown in FIG. 7, at 125℃, the resistance drift rate of the high-entropy structure thermistor is less than 1%, and the aging stability is excellent. Figure 1 Figure 3

[0047] ​​In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in combination with specific examples. The test materials and reagents used in the following examples, unless otherwise specified, can be obtained from commercial channels. If a specific technique or condition is not specified in the examples, it is a conventional method, which can be performed according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0048] Example 1

[0049] Step 1: Preparation of precursor powder

[0050] According to the molar ratio of La:Nd:Sm:Gd:Y:Mn = 1:1:1:1:1:5, oxide powders lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, yttrium trioxide and manganese dioxide were weighed and mixed to obtain a mixture; the mixture was placed in a ball mill tank, zirconium dioxide balls were used as the ball milling medium, and analytical pure anhydrous ethanol and deionized water were used as the dispersion medium for 8 hours of wet ball milling, and then the slurry after ball milling was dried at 60°C, and then taken out and ground in an agate mortar for 1 hour to obtain a precursor powder with yttrium trioxide as the oxide of RE.

[0051] Step 2: Preparation of perovskite phase powder

[0052] The precursor powder with yttrium trioxide as the oxide of RE was calcined at 1000°C for 2 hours, and then taken out and ground in an agate mortar for 1 hour to obtain a perovskite phase powder with yttrium trioxide as the oxide of RE.

[0053] Step 3: Preparation of high-entropy perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic

[0054] 0.5g of the perovskite phase powder with yttrium trioxide as the oxide of RE was weighed and poured into a die with a diameter of 10mm, a hydraulic machine was used with a pressure of 20 megapascals and a pressure holding time of 60 seconds to press into a perovskite phase formed block; the perovskite phase formed block was placed into a cold isostatic pressing machine for cold isostatic pressing with a pressure of 300 megapascals and a pressure holding time of 180 seconds to obtain a static pressure block; the perovskite phase static pressure block was sintered at a temperature of 1200°C for 12 hours to obtain a perovskite structure negative temperature coefficient thermosensitive ceramic with yttrium trioxide as the oxide of RE.

[0055] Structural performance parameters:

[0056] As shown in the diffraction peaks in the Figure 1 perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic with yttrium trioxide as the oxide of RE in Example 1 obtained by this method has a resistivity of 3388Ω·cm at a temperature of 0°C, and a material constant B -75 / 150℃ = 1960K. As shown in the Figure 2As shown in the resistance-temperature characteristic curve of the thermistor, the relationship between resistivity and temperature conforms to the Arrhenius equation, that is, as the temperature increases, the resistivity tends to decrease, which embodies the good negative temperature coefficient characteristic of the thermosensitive ceramic. Figure 3 As shown, the resistance drift rate of the negative temperature coefficient thermosensitive ceramic is relatively stable and remains within 1% within 500h at 125℃, which embodies good aging stability.

[0057] Example 2

[0058] Step 1: Preparation of precursor powder

[0059] According to the molar ratio of La:Nd:Sm:Gd:Ce:Mn = 1:1:1:1:1:5, oxide powders lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, cerium oxide and manganese dioxide were weighed and mixed to obtain a mixture; the mixture was placed in a ball mill tank, zirconium dioxide balls were used as the ball milling medium, and analytical pure anhydrous ethanol and deionized water were used as the dispersion medium for 9 hours of wet ball milling, and then the slurry after ball milling was dried at 70℃, and then taken out and ground in an agate mortar for 2 hours to obtain the precursor powder of RE oxide as cerium oxide.

[0060] Step 2: Preparation of perovskite phase powder

[0061] The precursor powder of RE oxide as cerium oxide was calcined at 1100℃ for 3 hours, taken out and ground in an agate mortar for 2 hours to obtain the perovskite phase powder of RE oxide as cerium oxide.

[0062] Step 3: Preparation of high-entropy perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic

[0063] 0.5g of the perovskite phase powder of RE oxide as cerium oxide was weighed and poured into a die with a diameter of 10mm, a hydraulic machine was used with a pressure of 20 megapascals and a pressure holding time of 60 seconds to press into a perovskite phase formed block; the perovskite phase formed block was placed into a cold isostatic pressing machine for cold isostatic pressing with a cold isostatic pressing pressure of 310 megapascals and a pressure holding time of 200 seconds to obtain a static pressure block; the perovskite phase static pressure block was sintered at a temperature of 1250℃ for 14 hours to obtain the perovskite structure negative temperature coefficient thermosensitive ceramic of RE oxide as cerium oxide.

[0064] Structural performance parameters:

[0065] As shown in the X-ray diffraction peaks, Figure 1 As shown in the X-ray diffraction peaks of the perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic of RE oxide as cerium oxide in Example 2 obtained by this method, the resistivity is 6473Ω·cm at a temperature of 0℃, and the material constant is B -75 / 150℃ = 2654K. Figure 2As shown in the resistance-temperature characteristic curve of the thermistor, the relationship between resistivity and temperature conforms to the Arrhenius equation, that is, as the temperature increases, the resistivity tends to decrease, which embodies the good negative temperature coefficient characteristic of the thermosensitive ceramic. Figure 3 As shown, the resistance drift rate of the negative temperature coefficient thermosensitive ceramic under the condition of 125℃ for 500h is relatively stable and remains within 1%, which embodies good aging stability.

[0066] Example 3

[0067] Step 1: Preparation of precursor powder

[0068] According to the molar ratio of La:Nd:Sm:Gd:Dy:Mn = 1:1:1:1:1:5, oxide powders lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, dysprosium trioxide and manganese dioxide were weighed and mixed to obtain a mixture; the mixture was placed in a ball mill tank, zirconium dioxide balls were used as the ball milling medium, and analytical pure anhydrous ethanol and deionized water were used as the dispersion medium for 10 hours of wet ball milling, and then the slurry after ball milling was dried at 80℃, and then taken out and ground in an agate mortar for 3 hours to obtain a precursor powder with RE oxide being dysprosium trioxide.

[0069] Step 2: Preparation of perovskite phase powder

[0070] The precursor powder with RE oxide being dysprosium trioxide was calcined at 1100℃ for 4 hours, taken out and ground in an agate mortar for 2 hours to obtain a perovskite phase powder with RE oxide being dysprosium trioxide.

[0071] Step 3: Preparation of high-entropy perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic

[0072] 0.5g of the perovskite phase powder with RE oxide being dysprosium trioxide was weighed and poured into a die with a diameter of 10mm, a hydraulic machine was used with a pressure of 20 megapascals and a pressure holding time of 60 seconds to press into a perovskite phase formed block; the perovskite phase formed block was placed into a cold isostatic pressing machine for cold isostatic pressing with a cold isostatic pressing pressure of 320 megapascals and a pressure holding time of 210 seconds to obtain a static pressure block; the perovskite phase static pressure block was sintered at a temperature of 1300℃ for 16 hours to obtain a perovskite structure negative temperature coefficient thermosensitive ceramic with RE oxide being dysprosium trioxide.

[0073] Structural performance parameters:

[0074] As shown in the X-ray diffraction peaks, Figure 1 the perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic with RE oxide being dysprosium trioxide in Example 3 obtained by this method has a resistivity of 3714Ω·cm at a temperature of 0℃, and a material constant B -75 / 150℃ = 2473K.Figure 2 As shown in the resistance-temperature characteristic curve of the thermistor, the relationship between resistivity and temperature conforms to the Arrhenius equation, that is, as the negative temperature increases, the resistivity also shows an upward trend, which embodies the good negative temperature coefficient characteristics of the thermosensitive ceramic. Figure 3 As shown, the resistance drift rate of the negative temperature coefficient thermosensitive ceramic is relatively stable and remains within 1% within 500h at 125℃, which embodies good aging stability.

[0075] Example 4

[0076] Step 1: Preparation of precursor powder

[0077] According to the molar ratio of La:Nd:Sm:Gd:Ho:Mn = 1:1:1:1:1:5, oxide powders lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, holmium trioxide and manganese dioxide were weighed and mixed to obtain a mixture; the mixture was placed in a ball mill tank, zirconium dioxide balls were used as the ball milling medium, and analytical pure anhydrous ethanol and deionized water were used as the dispersion medium for 11 hours of wet ball milling, and then the slurry after ball milling was dried at 90℃, and then taken out and ground in an agate mortar for 4 hours to obtain a precursor powder with RE oxide being holmium trioxide.

[0078] Step 2: Preparation of perovskite phase powder

[0079] The precursor powder with RE oxide being holmium trioxide was calcined at 1050℃ for 4 hours, taken out and ground in an agate mortar for 2 hours to obtain a perovskite phase powder with RE oxide being holmium trioxide.

[0080] Step 3: Preparation of high-entropy negative temperature coefficient thermosensitive ceramic with high-entropy perovskite structure

[0081] The perovskite phase powder with RE oxide being holmium trioxide was weighed and poured into a mold with a diameter of 10mm, the hydraulic machine used a pressure of 20 megapascals, and the pressure holding time was 60 seconds to press into a perovskite phase forming block; the perovskite phase forming block was placed into a cold isostatic pressing machine for cold isostatic pressing, the cold isostatic pressing pressure was 330 megapascals, and the pressure holding time was 220 seconds to obtain a static pressure block; the perovskite phase static pressure block was sintered at a temperature of 1250℃ for 18 hours to obtain a perovskite structure negative temperature coefficient thermosensitive ceramic with RE oxide being holmium trioxide.

[0082] Structural performance parameters:

[0083] As shown in the diffraction peaks in the range of 20°-80°, Figure 1 As shown in the diffraction peaks in the range of 20°-80°, the perovskite structure high-entropy negative temperature coefficient thermosensitive ceramic with RE oxide being holmium trioxide in Example 4 obtained by this method has a resistivity of 6807Ω·cm at a temperature of 0℃, and a material constant B -75 / 150℃=2454K. For example... Figure 2 As shown in the thermistor's temperature resistance characteristic curve, the relationship between resistivity and temperature conforms to the Arrhenius equation, that is, as the negative temperature increases, the resistivity also shows an upward trend, demonstrating that the thermistor ceramic has good negative temperature coefficient characteristics. Figure 3 As shown, the resistance drift rate of this negative temperature coefficient thermistor is relatively stable and remains within 1% within 500 hours under 125℃ conditions, demonstrating good aging stability.

[0084] Example 5

[0085] Step 1: Preparation of precursor powder

[0086] Lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, ytterbium trioxide, and manganese dioxide were weighed and mixed according to the molar ratio of La:Nd:Sm:Gd:Yb:Mn = 1:1:1:1:1:5 to obtain a mixture. The mixture was placed in a ball mill jar, and wet ball milling was performed for 12 hours using zirconium dioxide balls as the ball milling medium and analytical grade anhydrous ethanol and deionized water as the dispersion medium. The ball-milled slurry was then dried at 100°C and then placed in an agate mortar and ground for 4 hours to obtain the precursor powder of ytterbium trioxide as the oxide of RE.

[0087] Step 2: Preparation of perovskite phase powder

[0088] The precursor powder of RE oxide, which is ytterbium trioxide, was calcined at 1200℃ for 4 hours, then removed and ground in an agate mortar for 2 hours to obtain perovskite phase powder of RE oxide, which is ytterbium trioxide.

[0089] Step 3: Preparation of high-entropy negative temperature coefficient thermistors with high-entropy perovskite structure

[0090] 0.5g of perovskite phase powder with ytterbium trioxide as the oxide of RE was weighed and poured into a mold with a diameter of 10mm. The mold was pressed into a perovskite phase block using a hydraulic press at a pressure of 20 MPa and a holding time of 60 seconds. The perovskite phase block was then placed in a cold isostatic press for cold isostatic pressing at a pressure of 350 MPa and a holding time of 240 seconds to obtain a statically pressed block. The perovskite phase statically pressed block was then sintered at 1350℃ for 24 hours to obtain a perovskite structure negative temperature coefficient thermistor ceramic with ytterbium trioxide as the oxide of RE.

[0091] Structural performance parameters:

[0092] like Figure 1 As shown by the diffraction peaks, this method yielded a perovskite-structured, high-entropy, negative temperature coefficient thermistor ceramic with ytterbium trioxide as the oxide of RE in Example 5. The resistivity at 0°C was 2122 Ω·cm, and the material constant was B.-75 / 150℃ =2488K. For example... Figure 2 As shown in the thermistor's temperature resistance characteristic curve, the relationship between resistivity and temperature conforms to the Arrhenius equation, that is, as the negative temperature increases, the resistivity also shows an upward trend, demonstrating that the thermistor ceramic has good negative temperature coefficient characteristics. Figure 3 As shown, the resistance drift rate of this negative temperature coefficient thermistor is relatively stable and remains within 1% within 500 hours under 125℃ conditions, demonstrating good aging stability.

[0093] Comparative Example 1

[0094] LaMnO3 perovskite structural and performance parameters:

[0095] Material constants B of LaMnO3 perovskite -75 / 150℃ =314K, resistivity ρ 0℃ = 14Ω·cm. For example... Figure 4 As shown in the thermistor's temperature resistance characteristic curve, the resistivity increases with increasing negative temperature, but the rate of increase is relatively slow, and the fitting effect is not obvious, exhibiting negative temperature coefficient characteristics. Figure 5 As shown, at 125℃, the resistivity drift rate of LaMnO3 perovskite increases rapidly. Within 500 hours, the resistivity drift rate continues to rise to 1% to 5% as the temperature increases, indicating that LaMnO3 perovskite has poor aging stability.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perovskite-structured high-entropy negative temperature coefficient thermistor ceramic, wherein the chemical formula of the high-entropy negative temperature coefficient thermistor ceramic is (La... 0.2 Nd 0.2 Sm 0.2 Gd 0.2 RE 0.2 MnO3, where, RE is one of Ce, Dy, Ho, Yb, and Sc. The resistivity of the high-entropy negative temperature coefficient thermistor ceramic is ρ0℃=2122Ω·cm ~6807Ω·cm, the applicable temperature range is -75℃~150℃, and the material constant B-75 / 150℃=1960 K~2654 K.

2. The perovskite-structured high-entropy negative temperature coefficient thermistor ceramic according to claim 1, wherein the high-entropy negative temperature coefficient thermistor ceramic is formed by sintering a mixture of oxides of lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, and RE with manganese dioxide, wherein, The oxide of RE is cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide, or scandium trioxide.

3. The perovskite-structured high-entropy negative temperature coefficient thermistor ceramic according to claim 1, wherein the high-entropy negative temperature coefficient thermistor ceramic, after aging for 500 hours at -75℃ to 150℃, exhibits a resistivity drift of less than 1%.

4. A method for preparing perovskite-structured high-entropy negative temperature coefficient thermistor ceramics according to any one of claims 1-3, comprising: Lanthanum trioxide, neodymium trioxide, samarium trioxide, gadolinium trioxide, the oxide of the aforementioned RE, and manganese dioxide are mixed and then subjected to wet milling, drying, and grinding processes in sequence to obtain precursor powder; wherein, the oxide of the RE is cerium dioxide, dysprosium trioxide, holmium trioxide, ytterbium trioxide, or scandium trioxide; The precursor powder is calcined and ground into powder to obtain perovskite phase powder; The perovskite phase powder was sequentially pressed and sintered to obtain the perovskite-structured high-entropy negative temperature coefficient thermistor ceramic.

5. The preparation method according to claim 4, wherein, The molar ratio of La:Nd:Sm:Gd:RE:Mn in the perovskite-structured high-entropy negative temperature coefficient thermistor ceramic is 1:1:1:1:1:

5.

6. The preparation method according to claim 4, wherein, The operation of pressing the perovskite phase powder into shape includes: The perovskite phase powder is pressed into blocks and then subjected to cold isostatic pressing to obtain statically pressed blocks.

7. The preparation method according to claim 4, wherein, The calcination temperature is 1000~1200℃, and the calcination time is 2~4h.

8. The preparation method according to claim 6, wherein, The cold isostatic pressing pressure is 300~350MPa, and the holding time is 180~240s.

9. The preparation method according to any one of claims 4-8, wherein, The sintering temperature is 1200~1350℃, and the sintering time is 12~24h.

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