A negative temperature coefficient medium entropy thermistor material, preparation method and application thereof

Abstract

The present invention discloses a negative temperature coefficient medium-entropy thermistor material, a preparation method thereof, and an application thereof. The present invention uses manganese dioxide, nickel oxide, cobalt sesquioxide, zinc oxide, and copper oxide as raw materials, and adopts a solid-phase reaction method to prepare a negative temperature coefficient medium-entropy thermistor material with a chemical formula of (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4. The values of X1, X2, X3, and X4 are 0.075 to 0.425, and X1 + X2 + X3 + X4 = 1. The negative temperature coefficient medium-entropy thermistor material of the present invention has a single spinel structure. The material has both the hysteresis diffusion effect of medium-entropy ceramics, and combines the coordinated optimization effect among multiple components, which can significantly reduce the material constant and resistivity of the thermistor ceramics and improve the anti-aging performance.

Description

Technical Field

[0001] The present invention belongs to the field of thermistor materials, and relates to a negative temperature coefficient medium entropy thermistor material, a preparation method and applications thereof, and in particular to a spinel phase negative temperature coefficient medium entropy thermistor material suitable for low temperature, a preparation method and applications thereof. Background Art

[0002] The development of low-temperature physics technology and space technology has put forward higher requirements for temperature monitoring and control of negative temperature coefficient thermistors (NTC thermistors) in low-temperature environments. For NTC thermistors for low-temperature temperature detection, the resistance of the NTC thermistor must not be higher than a certain allowable value. As the temperature decreases, materials with a smaller thermistor constant B must be selected. Therefore, in order to reduce the B value, NTC thermistors for low temperatures often add elements with good conductive properties, such as Cu, but this will bring about serious aging.

[0003] The aging phenomenon of NTC thermistors is manifested as a change in the resistance value of the resistor material, which affects the working performance of the resistor material. The causes of aging, such as the composition of thermistor ceramic materials, the choice of sintering process, and the preparation of electrodes, will affect the stability of thermistor ceramic materials. Exploring different aging mechanisms and proposing improvement measures can improve the stability of NTC ceramics. MM Vakiv et al. (Journal of the European Ceramic Society, 2004, 24(6)) studied the aging mechanism of Cu 0.1 Ni 0.8 Co 0.2 Mn 1.9 The aging behavior of O4 spinel NTC ceramics at 170°C for 500h was studied, and it was pointed out that the presence of a small amount of additional phase is very helpful in slowing down the aging of thermistor ceramics. At the same time, the variable valence cations in the thermistor lattice tend to be oriented to reduce distortion. During the high-temperature sintering process, the directional arrangement will be destroyed, and the non-equilibrium state will continue during the cooling process, and gradually transform to equilibrium in the subsequent process. The rearrangement of cations causes the resistance value of the thermistor material to shift due to aging.

[0004] High entropy alloy materials (HEAs) born from the concept of high entropy, with their thermodynamic high entropy effect, kinetic slow diffusion effect, structural lattice distortion effect and performance "cocktail effect", show excellent performance that many traditional materials cannot match. If thermistors are designed with high entropy, the radii of various ions vary greatly, and it is difficult to form a single phase, which puts strict requirements on the sintering process of the materials. Medium entropy ceramics have a kinetic slow diffusion effect, and the effective diffusion rate of cations in the structure of thermistor materials will be greatly reduced, and their distribution will be more stable, so the aging performance of medium entropy thermistors will be greatly improved. Summary of the invention

[0005] In view of this, the present invention provides a negative temperature coefficient medium entropy thermistor material, a preparation method and its application, and provides a thermistor material that can effectively slow down atomic diffusion and reduce material constants and aging mobility. The present invention expands the test temperature zone to low temperature by adding copper oxide, and has the characteristics of simple preparation process; the material is a low resistance and low B value material, suitable for low temperature temperature measurement and control and alarm, and has the characteristics of good stability, overcoming the core problems of existing low temperature thermistor elements with large resistance and poor stability.

[0006] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0007] On the one hand, the present invention provides a negative temperature coefficient medium entropy thermistor material, the chemical formula of which is (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4; wherein the values ​​of X1, X2, X3, and X4 are 0.025~0.475, and X1+X2+X3+X4=1.

[0008] Another aspect of the present invention further provides a method for preparing the above-mentioned negative temperature coefficient medium entropy thermistor material, comprising the following steps:

[0009] 1) Weigh raw materials manganese dioxide, nickel oxide, cobalt trioxide, zinc oxide and copper oxide in proportion; wherein the molar ratio of the raw materials is 2: X1: X2: X3: X4, calculated as metal elements, and the values ​​of X1, X2, X3 and X4 are 0.025-0.475, and X1+X2+X3+X4=1;

[0010] 2) Add nickel oxide, cobalt trioxide, zinc oxide and copper oxide in sequence, and add manganese dioxide after mixing for 1-3 hours;

[0011] 3) placing the mixture obtained in step 2) in a polytetrafluoroethylene tank, adding agate balls and a dispersant for ball milling to obtain a mixed powder;

[0012] 4) Calcine the mixed powder in air atmosphere to obtain (Ni X1 Co X2 Zn X3 Cu X4 ) Mn2O4 calcined material; calcination is used to remove impurities;

[0013] 5) The calcined (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 calcined material was added to an agate mortar and ground to obtain (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder; then (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder briquettes;

[0014] 6) After the briquetting (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 block is placed in the buried powder and sintered to obtain a chemical formula of (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 negative temperature coefficient medium entropy thermistor material.

[0015] The final chemical formula is (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 negative temperature coefficient medium entropy thermistor material is a ceramic material with a single spinel structure. The material has the hysteresis diffusion effect of medium entropy ceramics, combined with the coordinated optimization effect between multiple components, which can significantly reduce the material constant and resistivity of the thermistor ceramics and improve the anti-aging performance.

[0016] In some specific implementations, in step 3), the mass ratio of the mixture, agate balls and dispersant is 1:1:4; and the ball milling time is 12-18 hours.

[0017] In some specific embodiments, the dispersant is a mixture of anhydrous ethanol and glycerol; wherein the mixing volume ratio of anhydrous ethanol to glycerol is (1-9):(1-9).

[0018] In some specific embodiments, the calcination temperature in step 4) is 750-950° C., and the calcination time is 2-4 hours.

[0019] In some specific embodiments, the briquetting in step 5) comprises the following steps:

[0020] The (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder is uniaxially pressed into blocks at a pressure of 0.5-2MPa for 30-90s.

[0021] In some specific embodiments, the briquetting in step 5) further comprises cold isostatic pressing at a pressure of 320 MPa for 150-180 seconds to obtain a 10×1.4 mm block.

[0022] In some specific embodiments, the sintering temperature in step 6) is 1050° C.-1200° C., and the sintering time is 4-7 hours.

[0023] In some specific embodiments, the calcined powder in step 6) is MgO·Al2O3 powder.

[0024] Another aspect of the present invention provides an application of the above-mentioned negative temperature coefficient medium entropy thermistor material, wherein the chemical formula is (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4's negative temperature coefficient medium entropy thermistor material is used for temperature measurement and control, especially for temperature measurement and control at low temperatures.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] 1. (Ni X1 Co X2 Zn X3 Cu X4 ) In Mn2O4 materials, zinc ions are monovalent ions and have no conductivity. Increasing the zinc content effectively increases the resistivity of the system; while Cu + / Cu 2+ It is a variable valence ion with low activation energy, which can greatly reduce the resistivity of the system and realize effective temperature measurement and control at low temperatures.

[0027] 2. The medium-entropy thermistor material of the present invention has a kinetic slow diffusion effect, which can allow the thermistor ceramic to maintain good stability and improve the material's anti-aging properties.

[0028] 3. The melting point of the MgO·Al2O3 powder used for burial firing in the present invention is about 2200°C. The powder does not have a volatile characteristic at a sintering temperature of 1050°C-1200°C. At the same time, the powder has a low thermal expansion coefficient and a high thermal conductivity, which can enable the NTC thermistor material to be evenly heated in the spinel powder.

[0029] 4. The thermal element made of medium entropy thermistor is measured and controlled within the temperature range of -120-25℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A (Ni) provided in Example 1 of the present invention X1 Co X2 Zn X3 Cu X4 ) X-ray diffraction spectrum of Mn2O4 negative temperature coefficient medium entropy thermosensitive material;

[0031] Figure 2 A (Ni) provided in Example 1 of the present invention X1 Co X2 Zn X3 Cu X4 )Scanning electron microscope image of Mn2O4 negative temperature coefficient medium entropy thermistor ceramic;

[0032] Figure 3 A (Ni) provided in Example 1 of the present invention X1 Co X2 Zn X3 Cu X4 ) EDS images of each element in Mn2O4 negative temperature coefficient medium entropy thermistor ceramics;

[0033] Figure 4 Aging resistance shift rate diagram of NCZCM and NCZM negative temperature coefficient medium entropy thermistors prepared in Examples 1 to 4 and Comparative Example 1 provided by the present invention;

[0034] Figure 5 The (Ni X1 Co X2 Zn X3 Cu X4 Fe X5 )X-ray diffraction spectrum of Mn2O4 (NCZCFM) low-temperature medium-entropy thermistor ceramics. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0036] On the one hand, the embodiment of the present invention provides a medium entropy thermistor material, the chemical formula of which is (Ni X1 Co X2 ZnX3 Cu X4 )Mn2O4; wherein the values ​​of X1, X2, X3, and X4 are 0.025~0.475, and X1+X2+X3+X4=1.

[0037] The raw materials are manganese dioxide, nickel oxide, cobalt trioxide, zinc oxide and copper oxide; the molar ratio of the raw materials is 2: X1: X2: X3: X4, calculated as metal elements; the values ​​of X1, X2, X3 and X4 are 0.075-0.425, and X1+X2+X3+X4=1.

[0038] The present invention (Ni X1 Co X2 Zn X3 Cu X4 ) In Mn2O4 negative temperature coefficient medium entropy thermistor material (abbreviated as NCZCM), Cu + / Cu 2+ It is a mutable valence ion with low activation energy, which can greatly reduce the resistivity of the system and realize effective temperature measurement and control at low temperatures; the medium-entropy thermistor material has a kinetically slow diffusion effect, which can allow thermistor ceramics to maintain good stability and improve the material's anti-aging properties.

[0039] On the other hand, an embodiment of the present invention further provides a method for preparing a medium-entropy thermistor material, comprising the following steps:

[0040] Making a mixture of various oxides;

[0041] The mixture is placed in a polytetrafluoroethylene tank, and agate balls and a dispersant are added for ball milling to obtain a mixed powder;

[0042] The mixed powder was calcined in air to obtain (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 calcined material;

[0043] After calcination, (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 calcined material was added to an agate mortar and ground to obtain (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder.

[0044] Finally, X1 Co X2 Zn X3 CuX4 )Mn2O4 powder is pressed into a block and sintered to obtain the negative temperature coefficient medium entropy thermistor material of the present invention.

[0045] Example 1

[0046] 101. Add 1.4632g of nickel oxide, 1.6244g of cobalt trioxide, 1.594g of zinc oxide and 1.558g of copper oxide in sequence. After mixing for 1 hour, add 13.7605g of manganese dioxide and mix; it is calculated that the molar ratio of Ni, Co, Zn, Cu and Mn elements is 0.25: 0.25: 0.25: 0.25: 2.

[0047] 102. The obtained mixture was placed in a polytetrafluoroethylene tank, and agate balls and dispersant were added for ball milling (the mass ratio of the mixture, agate balls and dispersant was 1:1:4, and the mixed volume ratio of anhydrous ethanol and glycerol in the dispersant was 1:9). The mixed powder was obtained by ball milling for 12 hours.

[0048] 103. The mixed powder was calcined at 750°C in air for 2 h to obtain (Ni 0.25 Co 0.25 Zn 0.25 Cu 0.25 )Mn2O4 calcined material.

[0049] 104. 0.25 Co 0.25 Zn 0.25 Cu 0.25 )Mn2O4 calcined material was put into an agate mortar and ground to obtain (Ni 0.25 Co 0.25 Zn 0.25 Cu 0.25 )Mn2O4 powder was uniaxially pressed at a pressure of 0.5 MPa for 30 s, and further cold isostatically pressed at 320 MPa for 150 s to obtain a Ф10×1.4 mm block.

[0050] 105. The formed block is placed in the calcined MgO·Al2O3 powder and sintered at 1150℃ for 4h to obtain a negative temperature coefficient medium entropy thermistor material, whose chemical formula is (Ni 0.25 Co 0.25 Zn 0.25 Cu 0.25 )Mn2O4.

[0051] 106. Slice the ceramic block, screen print silver-palladium paste, burn the electrode at 835℃ for 30min, and conduct the conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip is obtained; after welding the leads, place it in a constant temperature oil tank and measure the resistance value-temperature at -120-25℃. The NCZCM-S1 thermistor element is aged in an oven at 50℃ for 800h to obtain the aging resistance offset rate , where R1 and R0 are the resistance values ​​of the component before and after aging at 50°C, respectively.

[0052] The negative temperature coefficient medium entropy thermistor material prepared in Example 1 is represented by the code NCZCM-S1. Figure 1 As shown, the diffraction peaks located at 18.3°, 30.1°, 35.5°, 37.1°, 43.2°, 53.5°, 57.1°, 62.7° and 74.1° correspond to the characteristic peaks of cubic NiMn2O4 (PDF#01-0110, Fd-3m space group).

[0053] like Figure 2 As shown by Figure 2 It can be seen that NCZCM-S1 is composed of uniform grains and grain boundaries, and from the surface morphology, there are no obvious cracks and holes, which indicates that a relatively dense ceramic body is prepared in Example 1. The overall grain size distribution range is 1.4-2.6 μm, and is normally distributed.

[0054] like Figure 3 As shown in the figure, the EDS spectra of Mn, Zn, Co, Ni, Cu, and O of NCZCM-S1 show that Mn, Zn, Co, Ni, and Cu are evenly distributed in the region without obvious segregation or enrichment. The oxygen element has a relatively obvious boundary. Due to a certain height difference at the grain boundary, it has little effect on the characteristic X-ray diffraction intensity of heavy elements (Mn, Zn, Co, Ni, and Cu), but has a more significant effect on the X-ray diffraction intensity of light elements (O). The results show that the prepared powder is a medium entropy ceramic powder.

[0055] In this embodiment, a uniaxial pressing method is used to press the powder, cold isostatically press and sinter the powder to form (Ni 0.25 Co 0.25 Zn 0.25 Cu 0.25 )Mn2O4 medium entropy thermistor material, using NCZCM with medium entropy stability as the material of the thermistor element, Cu in NCZCM + / Cu 2+It is a variable valence ion that can greatly reduce the resistivity of the system and realize effective temperature measurement and control at low temperatures; the medium-entropy thermistor material has a kinetic slow diffusion effect, which can improve the material's anti-aging properties.

[0056] Example 2

[0057] The embodiment of the present invention provides a second method for preparing a medium-entropy thermistor material, comprising the following steps:

[0058] 201. 1.4642 g of nickel oxide, 1.6255 g of cobalt trioxide, 0.9571 g of zinc oxide and 2.1827 g of copper oxide were added in sequence. After mixing for 1.5 hours, 13.7704 g of manganese dioxide was added and mixed. According to calculation, the molar ratio of Ni, Co, Zn, Cu and Mn elements was 0.25: 0.25: 0.15: 0.35: 2.

[0059] 202. The obtained mixture was placed in a polytetrafluoroethylene tank, and agate balls and a dispersant were added for ball milling (the mass ratio of the mixture, agate balls and dispersant was 1:1:4, and the mixed volume ratio of anhydrous ethanol and glycerol in the dispersant was 3:7). The mixed powder was obtained by ball milling for 14 hours.

[0060] 203. The mixed powder was calcined at 800°C in air for 2.5 h to obtain (Ni 0.25 Co 0.25 Zn 0.15 Cu 0.35 )Mn2O4 calcined material.

[0061] 204. 0.25 Co 0.25 Zn 0.15 Cu 0.35 )Mn2O4 calcined material was ground in an agate mortar to obtain (Ni 0.25 Co 0.25 Zn 0.15 Cu 0.35 )Mn2O4 powder was uniaxially pressed at a pressure of 1 MPa for 50 s, and further cold isostatically pressed at 320 MPa for 160 s to obtain a Ф10×1.4 mm block.

[0062] 205. The formed block was placed in the calcined (MgO·Al2O3) powder and sintered at 1050℃ for 4.5h to obtain the negative temperature coefficient medium entropy thermistor material NCZCM-S2, the chemical formula of which is (Ni 0.25 Co 0.25 Zn 0.15 Cu 0.35 )Mn2O4.

[0063] 206. Slice the ceramic block, screen print silver-palladium paste, burn the electrode at 835℃ for 30min, and conduct the conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip is obtained; after welding the leads, place it in a constant temperature oil tank and measure the resistance value-temperature at -120-25℃. The NCZCM-S2 thermistor element is aged in an oven at 50℃ for 800h to obtain the aging resistance offset rate , where R1 and R0 are the resistance values ​​of the component before and after aging at 50°C, respectively.

[0064] Example 3

[0065] The embodiment of the present invention provides a third method for preparing a medium-entropy thermistor material, comprising the following steps:

[0066] 301. 1.4648 g of nickel oxide, 1.6261 g of cobalt trioxide, 0.6383 g of zinc oxide and 2.4954 g of copper oxide were added in sequence. After mixing for 2 hours, 13.7754 g of manganese dioxide was added and mixed. According to calculation, the molar ratio of Ni, Co, Zn, Cu and Mn elements was 0.25: 0.25: 0.1: 0.4: 2.

[0067] 302. The obtained mixture is placed in a polytetrafluoroethylene tank, and agate balls and dispersant are added for ball milling (the mass ratio of the three is 1:1:4, and the mixed volume ratio of anhydrous ethanol and glycerol in the dispersant is 7:3), and the mixed powder is obtained by ball milling for 16 hours.

[0068] 303. The mixed powder was calcined at 850°C for 3 h in air atmosphere to obtain (Ni 0.25 Co 0.25 Zn 0.1 Cu 0.4 )Mn2O4 calcined material.

[0069] 304. 0.25 Co 0.25 Zn 0.1 Cu 0.4 )Mn2O4 calcined material was ground in an agate mortar to obtain (Ni 0.25 Co 0.25 Zn 0.1 Cu 0.4 )Mn2O4 powder was uniaxially pressed at a pressure of 1.5 MPa for 70 s, and further cold isostatically pressed at 320 MPa for 170 s to obtain a Ф10×1.4 mm block.

[0070] 305. The formed block was placed in the calcined MgO·Al2O3 powder and sintered at 1100℃ for 5h to obtain the negative temperature coefficient medium entropy thermistor material NCZCM-S3, the chemical formula of which is (Ni 0.25 Co 0.25 Zn 0.1 Cu 0.4 )Mn2O4.

[0071] 306. Slice the ceramic block, screen print silver-palladium paste, burn the electrode at 835℃ for 30min, and conduct the conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip is obtained; after welding the lead wire, place it in a constant temperature oil tank and measure the resistance value-temperature at -120-25℃. The NCZCM-S3 thermistor element is aged in an oven at 50℃ for 800h to obtain the aging resistance offset rate , where R1 and R0 are the resistance values ​​of the component before and after aging at 50°C, respectively.

[0072] Example 4

[0073] The embodiment of the present invention provides a fourth method for preparing a medium-entropy thermistor material, comprising the following steps:

[0074] 401. Add 1.465g nickel oxide, 1.6264g cobalt trioxide, 0.4788g zinc oxide and 2.6519g copper oxide in sequence, mix for 3 hours, and then add 13.779g manganese dioxide for mixing; according to calculation, the molar ratio of Ni, Co, Zn, Cu and Mn elements is 0.25: 0.25: 0.075: 0.425: 2.

[0075] 402. The obtained mixture is placed in a polytetrafluoroethylene tank, and agate balls and a dispersant are added for ball milling (the mass ratio of the three is 1:1:4, and the mixed volume ratio of anhydrous ethanol and glycerol in the dispersant is 9:1), and the mixed powder is obtained by ball milling for 18 hours.

[0076] 403. The mixed powder was calcined at 950°C in air for 4 h to obtain (Ni 0.25 Co 0.25 Zn 0.075 Cu 0.425 )Mn2O4 calcined material.

[0077] 404、Will 0.25 Co 0.25 Zn 0.075 Cu 0.425 )Mn2O4 calcined material was ground in an agate mortar to obtain (Ni 0.25 Co 0.25 Zn 0.075Cu 0.425 )Mn2O4 powder was uniaxially pressed at a pressure of 2MPa for 90s, and further cold isostatically pressed at 320MPa for 180s to obtain a Ф10×1.4mm block.

[0078] 405. The formed block is placed in the calcined MgO·Al2O3 powder and sintered at 1200℃ for 7h to obtain the negative temperature coefficient medium entropy thermistor material NCZCM-S4, the chemical formula of which is (Ni 0.25 Co 0.25 Zn 0.075 Cu 0.425 )Mn2O4.

[0079] 406. Slice the ceramic block, screen print silver-palladium paste, burn the electrode at 835℃ for 30min, and conduct the conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip is obtained; after welding the lead wire, place it in a constant temperature oil tank and measure the resistance value-temperature at -120-25℃. The NCZCM-S4 thermistor element is aged in an oven at 50℃ for 800h to obtain the aging resistance offset rate , where R1 and R0 are the resistance values ​​of the component before and after aging at 50°C, respectively.

[0080] Comparative Example 1

[0081] The difference between this comparative example 1 and the example 1 is that 1.9493 g of nickel oxide, 2.164 g of cobalt oxide and 2.1236 g of zinc oxide are fully mixed, and then uniformly mixed with 13.7631 g of manganese oxide. The chemical formula of the obtained medium entropy thermistor material is (Ni 1 / 3 Co 1 / 3 Zn 1 / 3 )Mn2O4, represented by the code NCZM.

[0082] The ceramic block was sliced, silver-palladium paste was screen-printed, and the electrode was burned at 835℃ for 30 minutes for conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip was obtained; after welding the leads, it was placed in a constant temperature oil tank and the resistance value-temperature was measured at -120-25℃. The NCZM thermistor element was aged in an oven at 50℃ for 800h to obtain the aging resistance offset rate , where R1 and R0 are the resistance values ​​of the component before and after aging at 50°C, respectively.

[0083] Comparative Example 2

[0084] The difference between this comparative example 2 and the example 1 is that 1.2515 g of nickel oxide, 1.3893 g of cobalt oxide, 1.3634 g of zinc oxide, 1.3326 g of copper oxide and 1.3375 g of ferric oxide are fully mixed, and then uniformly mixed with 13.3256 g of manganese oxide. The chemical formula of the high entropy thermistor material obtained is (Ni 0.2 Co 0.2 Zn 0.2 Cu 0.2 Fe 0.2 )Mn2O4, represented by the code NCZCFM.

[0085] The ceramic block was sliced, silver-palladium paste was screen printed, and the electrode was fired at 835℃ for 30 minutes to conduct the conductive operation. After slicing, a 1.0mm×1.0mm×0.35mm thermistor chip was obtained; after welding the leads, it was placed in a constant temperature oil bath and the resistance value-temperature was measured at -120-25℃.

[0086] like Figure 4 As shown, from the aging resistance shift rate diagram of NCZCMS1-S4, NCZM, and NCZCFM low-temperature medium-entropy thermistors prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2, it can be seen that the resistance aging shift rate of the NCZCMS1 sample is the smallest, which is 0.6%, and the resistance aging shift rate of NCZM is the largest, which is 7.8%.

[0087] The resistivity ρ of the six thermistors NCZCMS1-S4, NCZM and NCZCFM were obtained. -80℃ and B -80 / -30℃ The values ​​range from 3964 to 3017534Ω·cm and 2177 to 3561K. Among them, NCZCMS1 has the lowest resistivity of 3964Ω·cm, the smallest material constant of 2177K, and the best anti-aging performance (the resistance shift rate is only 0.6%, much lower than 7.8% of NCZM). It can be seen that compared with other thermistors, NCZCMS1 is particularly suitable for low temperature measurement and control, as well as stable measurement.

[0088] like Figure 5 As shown, the XRD spectrum of NCZCFM material shows that the diffraction peaks at 18.3°, 30.1°, 35.5°, 37.1°, 43.2°, 53.5°, 57.1°, 62.7° and 74.1° correspond to the characteristic peaks of cubic NiMn2O4 (PDF#01-0110, Fd-3m space group). The peaks at 29.7°, 33.4° and 60.8° are impurity peaks, indicating the appearance of a second phase, indicating that when the component is 5, the material has a dual-phase structure.

[0089] It can be seen from the above examples 1 to 4, comparative examples 1 and 2 that the material constant B and resistivity of the thermistor element made of NCZCM-S1 in example 1 are 2177K and 3964Ω·cm respectively, and its aging resistance shift rate at high temperature is 0.6%. The NCZCM medium entropy thermistor material is formed by mixing and reacting multiple oxides by a solid phase mixing method, Cu + / Cu 2 + The resistivity of the system can be greatly reduced, and effective temperature measurement and control at low temperatures can be achieved; medium-entropy thermistor materials have a kinetically slow diffusion effect, which can improve the material's anti-aging properties.

[0090] On the other hand, an embodiment of the present invention further provides an application of a NCZCM medium-entropy thermistor material, wherein the medium-entropy thermistor material is used for measuring and controlling a temperature environment, especially a temperature at a low temperature.

[0091] The NCZCM medium entropy thermistor material prepared by the present invention can have a low material constant, a low resistivity and a small aging resistance deviation rate as a thermal element material.

[0092] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A negative temperature coefficient medium entropy thermistor material, characterized in that: It is a spinel phase ceramic material with the chemical formula (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4; wherein the values ​​of X1, X2, X3, and X4 are 0.025~0.475, and X1+X2+X3+X4=1.

2. A method for preparing the negative temperature coefficient medium entropy thermistor material according to claim 1, characterized in that: The following steps are involved: 1) Weigh raw materials manganese dioxide, nickel oxide, cobalt trioxide, zinc oxide and copper oxide in proportion; wherein the molar ratio of the raw materials is 2: X1: X2: X3: X4, calculated as metal elements, and the values ​​of X1, X2, X3 and X4 are 0.025-0.475, and X1+X2+X3+X4=1; 2) Add nickel oxide, cobalt trioxide, zinc oxide and copper oxide in sequence, and add manganese dioxide after mixing for 1-3 hours; 3) placing the mixture obtained in step 2) in a polytetrafluoroethylene tank, adding agate balls and a dispersant for ball milling to obtain a mixed powder; 4) Calcine the mixed powder in air atmosphere to obtain (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 calcined material; 5) The calcined (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 calcined material was added to an agate mortar and ground to obtain (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder; then (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder briquettes; 6) After the briquetting (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 block is placed in the buried powder and sintered to obtain a chemical formula of (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 negative temperature coefficient medium entropy thermistor material.

3. The preparation method according to claim 2, characterized in that: In the step 3), the mass ratio of the mixture, agate balls and dispersant is 1:1:4; and the ball milling time is 12-18 hours.

4. The preparation method according to claim 3, characterized in that: The dispersant is a mixture of anhydrous ethanol and glycerol; wherein the mixing volume ratio of anhydrous ethanol to glycerol is (1-9):(1-9).

5. The preparation method according to claim 2, characterized in that: The calcination temperature of step 4) is 750-950° C., and the calcination time is 2-4 hours.

6. The preparation method according to claim 2, characterized in that: The briquetting in step 5) comprises the following steps: The (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4 powder is uniaxially pressed into blocks at a pressure of 0.5-2MPa for 30-90s.

7. The preparation method according to claim 6, characterized in that: The briquetting in step 5) further comprises cold isostatic pressing at a pressure of 320 MPa for 150-180 seconds to obtain a 10×1.4 mm block.

8. The preparation method according to claim 2, characterized in that: The sintering temperature in step 6) is 1050° C.-1200° C., and the sintering time is 4-7 hours.

9. The preparation method according to claim 2, characterized in that: The calcined powder in step 6) is MgO·Al2O3 powder.

10. An application of the negative temperature coefficient medium entropy thermistor material according to claim 1, characterized in that: The chemical formula is (Ni X1 Co X2 Zn X3 Cu X4 )Mn2O4's negative temperature coefficient medium entropy thermistor material is used for temperature measurement and control, especially for temperature measurement and control at low temperatures.

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