High-precision NTC thermistor and preparation method thereof

Abstract

The application discloses a high-precision NTC thermistor and a preparation method thereof, relates to the technical field of NTC thermistors, and improves the structural stability through a "cocktail effect"; high configuration entropy reduces the Gibbs free energy change of lattice deformation, inhibits lattice distortion under high temperature, greatly expands the temperature range of the prepared NTC thermistor, combines a multiple protection mechanism, further improves the anti-aging performance of the NTC thermistor in a high-temperature environment, greatly reduces the resistance drift rate in the high-temperature environment, and widens the application range of the NTC thermistor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of NTC thermistor, in particular to a high-precision NTC thermistor and a preparation method thereof. BACKGROUND

[0002] In the process of modern industry and rapid development of science and technology, many fields have put forward strict requirements for accurate temperature measurement and control. Especially in the metallurgy, special processing, automobile, aerospace and other industries, with the continuous upgrading of technology, the demand for accurate measurement and control of high temperature above 1000℃ is increasingly prominent. Negative temperature coefficient (NTC, Negative Temperature Coefficient) thermistor has become a potential high-temperature sensor solution with the advantages of high sensitivity, rapid response, simple structure and low cost, and has attracted much attention.

[0003] The core element of NTC thermistor is NTC thermistor ceramic, and its resistivity decreases exponentially with temperature rise. Common NTC thermistor ceramic is spinel structure or other structure oxide ceramic, which often contains one or more transition metal oxides such as CoO, NiO and MnO. According to the difference of chemical composition, the working temperature range of NTC thermistor is different, among which the use temperature range of high-temperature NTC thermistor ceramic is generally 300-1000℃, and the common ZrO2-Y2O3 system, ZrO2-CaO system fluorite structure material.

[0004] However, the current high-temperature NTC thermistor faces many challenges in practical application and performance improvement. On the one hand, if the thermistor is to be used in a super-wide temperature range of 25-1300℃ for a long time, the NTC thermistor ceramic needs to have high resistivity and appropriate material constant B value at high temperature. However, there is a positive correlation between resistivity and B value, and it is difficult to realize the coordinated reverse regulation of the two, which is a research problem in the field of NTC thermistor ceramic. On the other hand, when the applicable temperature rises, especially above 1000℃, the traditional high-temperature NTC thermistor ceramic is difficult to maintain stable performance and has poor high-temperature aging characteristics due to the change of conduction mechanism and serious distortion of crystal structure. For example, the NTC thermistor commonly made of manganese, chromium, iron and copper metal oxides is easy to decompose in high-temperature environment, which limits its maximum use temperature, and irreversible changes may occur even at slightly lower temperatures.

[0005] Therefore, it is of great significance to invent a high-precision NTC thermistor for its application in high-temperature environment. SUMMARY

[0006] The purpose of the present application is to provide a high-precision NTC thermistor and a preparation method thereof to solve the problems in the prior art.

[0007] To achieve the above object, the present application provides the following technical solutions:

[0008] A high-precision NTC thermistor, which is composed of a substrate layer, a sensitive layer, a protective layer and a sandwich protective layer from bottom to top; the substrate layer is alumina; the sensitive layer is prepared by printing a rare earth-based chromate slurry; the protective layer is prepared by printing a chromium oxide slurry; and the sandwich protective layer comprises an alumina sol layer and a glass-ceramic glaze layer.

[0009] Further, the preparation method of the rare earth-based chromate slurry comprises the following steps:

[0010] La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Cr2O3 are added into a ball mill tank, ethanol is used as a dispersant, and ball milling is performed for 8-10 h to obtain a slurry; the slurry is vacuum dried at 100-105 DEG C, ground, heated to 1100-1105 DEG C, pre-sintered for 5-5.5 h, and ground to obtain a precursor powder; the precursor powder is added into polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a rare earth-based chromate slurry.

[0011] Further, in the preparation process of the precursor powder, the molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5; in the preparation process of the rare earth-based chromate slurry, the mass ratio of the precursor powder to polysilazane is (1-2):(3-4); and the particle size of the precursor powder is 3-5 mu m.

[0012] Further, the preparation method of the chromium oxide slurry comprises the following steps:

[0013] Chromium oxide is added into polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a chromium oxide slurry.

[0014] Further, in the preparation process of the chromium oxide slurry, the mass ratio of chromium oxide to polysilazane is 1:(1.5-2); and the particle size of the chromium oxide is 1-1.5 mu m.

[0015] Further, the thickness of the sensitive layer is 20-25 mu m; the thickness of the protective layer is 20-25 mu m; the thickness of the sandwich protective layer is 60 mu m; the thickness of the alumina sol layer is 15-20 mu m; and the thickness of the glass-ceramic glaze layer is 20-30 mu m.

[0016] A method for preparing a high-precision NTC thermistor includes the following steps: printing a rare-earth-based chromate paste onto the surface of a substrate layer, sintering it at 1550-1555℃ for 15-16 hours to obtain a sensitive layer; after cooling, printing a chromium oxide paste onto the surface of the sensitive layer, annealing it at 1300-1305℃ for 1-1.5 hours to obtain a protective layer; after cooling, spraying an alumina sol onto the surface of the protective layer, annealing it at 1100-1105℃ for 1-1.5 hours to obtain an alumina sol layer; after cooling, spraying a glass-ceramic glaze onto the surface of the alumina sol layer, annealing it at 1200-1205℃ for 0.5-1 hours to obtain a glass-ceramic glaze layer; after cooling, spraying an alumina sol onto the surface of the glass-ceramic glaze layer, annealing it at 1100-1105℃ for 1-1.5 hours, cooling, and obtaining a high-precision NTC thermistor by attaching a silver-palladium electrode and platinum wire leads.

[0017] Furthermore, the glass-ceramic glaze has a solid content of 10-40 wt%, with the remainder being deionized water.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention enhances structural stability through the "cocktail effect"; high configurational entropy reduces the Gibbs free energy change of lattice deformation, suppresses lattice distortion at high temperatures, and further improves its anti-aging performance in high-temperature environments, greatly reducing the resistance drift rate in high-temperature environments and broadening the application range of NTC thermistors.

[0020] 2. The sensitive layer prepared by this invention differs from traditional chromate ceramics in that its Cr-O bond length phrases LaCrO3 and YCrO3 have stronger bond energies, reducing Cr content. 3+ To Cr 4+ Oxidation of CrO 6 Octahedral distortion and CrO3 volatilization significantly reduce porosity and improve density, laying the foundation for stable operation in high-temperature environments.

[0021] 3. In order to further improve the stability of NTC thermistors at high temperatures, this invention uses polysilazane in the slurry to transform into SiOC ceramic under high temperature conditions, filling the gaps in the sensitive layer and further stabilizing the structure. At the same time, the chromium oxide protective layer can further inhibit the decomposition of sensitive layer particles and the overflow of chromium oxide at high temperatures, reducing material degradation at high temperatures.

[0022] 4、Further, the sandwich protective layer is designed based on the design principle of "combination of soft and hard", the self-repairing and barrier effect of the intermediate glass-ceramic glaze layer and the structural support and isolation effect of the upper and lower ceramic layers are utilized, the three-layer structure is closely combined without obvious gap, the gas diffusion and material migration are blocked through the densification of the glass layer, the volatilization and erosion of the glass layer under high temperature are solved through the stability of the ceramic layer, the oxidation, sublimation and structural damage of the sensitive material are inhibited, and finally the stable work of the sensor in the high-temperature environment above 1300 DEG C is realized.

[0023] The glass-ceramic glaze material can be melted at high temperature, can fill the pores and micro-cracks in the protective layer, form a dense and continuous structure, thereby block the inward diffusion of oxygen and the outward escape of sublimation products of the sensitive material, and reduce the oxidation and sublimation loss of the sensitive layer. At the same time, the stable crystal phase and amorphous phase ensure the structural stability under high temperature, and play the self-repairing and sealing function of the "soft" component. The high-melting-point aluminum oxide ceramic as the "hard" component provides structural support and thermal stability for the entire protective layer, preventing the loss of the intermediate glass layer due to volatilization under high temperature. The bottom layer can isolate the sensitive film from the molten glass, preventing the sensitive layer from being eroded by the glaze; the top layer can reduce the high-temperature volatilization of the glass layer, while enhancing the overall mechanical strength and wear resistance of the protective layer. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a structural schematic diagram of a high-precision NTC thermistor according to the present application;

[0025] 1, substrate layer, 2, sensitive layer, 3, protective layer, 4, sandwich protective layer, 5, aluminum oxide sol layer, 6, glass-ceramic glaze layer. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] Embodiment 1: A preparation method of a high-precision NTC thermistor, comprising the following steps: S1: adding La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Cr2O3 into a ball mill jar, taking ethanol as a dispersant, ball milling for 8h to obtain a slurry; placing the slurry in a vacuum drying oven at 100 DEG C, grinding, heating to 1100 DEG C and pre-sintering for 5h, grinding to obtain a precursor powder; adding the precursor powder into polysilazane, stirring uniformly, ultrasonic dispersion to obtain a rare earth-based chromate slurry.

[0028] The molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5 in the preparation process of the precursor powder; the mass ratio of the precursor powder:polysilazane is 1:3 in the preparation process of the rare earth-based chromate slurry; and the particle size of the precursor powder is 3 μm.

[0029] S2: The chromium oxide is added to the polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a chromium oxide slurry.

[0030] The mass ratio of the chromium oxide:polysilazane is 1:1.5 in the preparation process of the chromium oxide slurry; and the particle size of the chromium oxide is 1 μm.

[0031] S3: The rare earth-based chromate slurry is printed on the surface of the substrate layer 1, heated to 1550°C and sintered for 15 h to obtain a sensitive layer 2; after cooling, the chromium oxide slurry is printed on the surface of the sensitive layer 2, heated to 1300°C and annealed for 1 h to obtain a protective layer 3; after cooling, the aluminum oxide sol is sprayed on the surface of the protective layer 3, heated to 1100°C and annealed for 1 h to obtain an aluminum oxide sol layer 5; after cooling, the glass-ceramic glaze material is sprayed on the surface of the aluminum oxide sol layer 5, heated to 1200°C and annealed for 0.5 h to obtain a glass-ceramic glaze layer 6; after cooling, the aluminum oxide sol is sprayed on the surface of the glass-ceramic glaze layer 6, heated to 1100°C and annealed for 1 h, and cooled to obtain a high-precision NTC thermistor by attaching a silver-palladium electrode and a platinum wire lead;

[0032] The thickness of the sensitive layer is 20 μm; the thickness of the protective layer is 25 μm; the thickness of the aluminum oxide sol layer is 15 μm; and the thickness of the glass-ceramic glaze layer is 30 μm.

[0033] Embodiment 2: A preparation method of a high-precision NTC thermistor, comprising the following steps: S1: La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Cr2O3 are added to a ball mill tank, ethanol is used as a dispersant, and ball milling is performed for 8 h to obtain a slurry; the slurry is vacuum dried at 100°C, ground, heated to 1100°C and pre-sintered for 5 h, ground, and a precursor powder is obtained; the precursor powder is added to polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a rare earth-based chromate slurry.

[0034] The molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5 in the preparation process of the precursor powder; the mass ratio of the precursor powder:polysilazane is 2:4 in the preparation process of the rare earth-based chromate slurry; and the particle size of the precursor powder is 3 μm.

[0035] S2: The chromium oxide is added to the polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a chromium oxide slurry.

[0036] The mass ratio of the chromium oxide to the polysilazane is 1:1.5 in the preparation process of the chromium oxide slurry; and the particle size of the chromium oxide is 1 μm.

[0037] S3: printing the rare earth-based chromate slurry on the surface of the substrate layer 1, sintering at 1550 DEG C for 15 h, to obtain a sensitive layer 2; after cooling, printing the chromium oxide slurry on the surface of the sensitive layer 2, annealing at 1300 DEG C for 1 h, to obtain a protective layer 3; after cooling, spraying the alumina sol on the surface of the protective layer 3, annealing at 1100 DEG C for 1 h, to obtain an alumina sol layer 5; after cooling, spraying the glass-ceramic glaze on the surface of the alumina sol layer 5, annealing at 1200 DEG C for 0.5 h, to obtain a glass-ceramic glaze layer 6; after cooling, spraying the alumina sol on the surface of the glass-ceramic glaze layer 6, annealing at 1100 DEG C for 1 h, cooling, and obtaining the high-precision NTC thermistor by attaching a silver-palladium electrode and a platinum wire lead;

[0038] The thickness of the sensitive layer is 20 μm; the thickness of the protective layer is 25 μm; the thickness of the alumina sol layer is 15 μm; and the thickness of the glass-ceramic glaze layer is 30 μm.

[0039] Comparative Example 1: a preparation method of a high-precision NTC thermistor, comprising the following steps: S1: adding 0.6MgAl2O4-0.4LaCr 0.5 Mn 0.5 O3 precursor powder into polysilazane, stirring uniformly, and ultrasonic dispersion, to obtain a rare earth-based chromate slurry.

[0040] The mass ratio of the precursor powder to the polysilazane is 1:3 in the preparation process of the rare earth-based chromate slurry; and the particle size of the precursor powder is 3 μm.

[0041] S2: adding chromium oxide into polysilazane, stirring uniformly, and ultrasonic dispersion, to obtain a chromium oxide slurry.

[0042] The mass ratio of the chromium oxide to the polysilazane is 1:1.5 in the preparation process of the chromium oxide slurry; and the particle size of the chromium oxide is 1 μm.

[0043] S3: printing the rare earth-based chromate slurry on the surface of the substrate layer 1, sintering at 1550 DEG C for 15h, obtaining a sensitive layer 2; after cooling, printing the chromium oxide slurry on the surface of the sensitive layer 2, annealing at 1300 DEG C for 1h, obtaining a protective layer 3; after cooling, spraying the alumina sol on the surface of the protective layer 3, annealing at 1100 DEG C for 1h, obtaining an alumina sol layer 5; after cooling, spraying the glass-ceramic glaze on the surface of the alumina sol layer 5, annealing at 1200 DEG C for 0.5h, obtaining a glass-ceramic glaze layer 6; after cooling, spraying the alumina sol on the surface of the glass-ceramic glaze layer 6, annealing at 1100 DEG C for 1h, cooling, obtaining a high-precision NTC thermistor by attaching silver-palladium electrodes and platinum wire leads;

[0044] The thickness of the sensitive layer is 20 μm; the thickness of the protective layer is 20 μm; the thickness of the alumina sol layer is 15 μm; and the thickness of the glass-ceramic glaze layer is 30 μm.

[0045] Comparative Example 2: a preparation method of a high-precision NTC thermistor, comprising the following steps: S1: adding YCr 0.5 Mn 0.5 O3 precursor powder into polysilazane, stirring uniformly, ultrasonic dispersion, obtaining a rare earth-based chromate slurry.

[0046] In the preparation process of the rare earth-based chromate slurry, the mass ratio of the precursor powder to the polysilazane is 1:3; and the particle size of the precursor powder is 3 μm.

[0047] S2: adding chromium oxide into polysilazane, stirring uniformly, ultrasonic dispersion, obtaining a chromium oxide slurry.

[0048] In the preparation process of the chromium oxide slurry, the mass ratio of the chromium oxide to the polysilazane is 1:1.5; and the particle size of the chromium oxide is 1 μm.

[0049] S3: printing the rare earth-based chromate slurry on the surface of the substrate layer 1, sintering at 1550 DEG C for 15h, obtaining a sensitive layer 2; after cooling, printing the chromium oxide slurry on the surface of the sensitive layer 2, annealing at 1300 DEG C for 1h, obtaining a protective layer 3; after cooling, spraying the alumina sol on the surface of the protective layer 3, annealing at 1100 DEG C for 1h, obtaining an alumina sol layer 5; after cooling, spraying the glass-ceramic glaze on the surface of the alumina sol layer 5, annealing at 1200 DEG C for 0.5h, obtaining a glass-ceramic glaze layer 6; after cooling, spraying the alumina sol on the surface of the glass-ceramic glaze layer 6, annealing at 1100 DEG C for 1h, cooling, obtaining a high-precision NTC thermistor by attaching silver-palladium electrodes and platinum wire leads;

[0050] The thickness of the sensitive layer is 20 pm; the thickness of the protective layer is 20 pm; the thickness of the alumina sol layer is 15 pm; and the thickness of the glass-ceramic glaze layer is 30 pm.

[0051] The preparation method of the high-precision NTC thermistor comprises the following steps: S1: adding YCrO3 precursor powder into polysilazane, uniformly stirring, and ultrasonic dispersion to obtain a rare earth-based chromate slurry.

[0052] In the preparation process of the rare earth-based chromate slurry, the mass ratio of the precursor powder to the polysilazane is 1:3; and the particle size of the precursor powder is 3 pm.

[0053] S2: adding chromium oxide into polysilazane, uniformly stirring, and ultrasonic dispersion to obtain a chromium oxide slurry.

[0054] In the preparation process of the chromium oxide slurry, the mass ratio of the chromium oxide to the polysilazane is 1:1.5; and the particle size of the chromium oxide is 1 pm.

[0055] S3: printing the rare earth-based chromate slurry on the surface of the substrate layer 1, heating to 1550 DEG C and sintering for 15 h to obtain a sensitive layer 2; after cooling, printing the chromium oxide slurry on the surface of the sensitive layer 2, heating to 1300 DEG C and annealing for 1 h to obtain a protective layer 3; after cooling, spraying alumina sol on the surface of the protective layer 3, heating to 1100 DEG C and annealing for 1 h to obtain an alumina sol layer 5; after cooling, spraying glass-ceramic glaze on the surface of the alumina sol layer 5, heating to 1200 DEG C and annealing for 0.5 h to obtain a glass-ceramic glaze layer 6; after cooling, spraying alumina sol on the surface of the glass-ceramic glaze layer 6, heating to 1100 DEG C and annealing for 1 h, and cooling to obtain a high-precision NTC thermistor by attaching a silver-palladium electrode and a platinum wire lead.

[0056] The thickness of the sensitive layer is 20 pm; the thickness of the protective layer is 20 pm; the thickness of the alumina sol layer is 15 pm; and the thickness of the glass-ceramic glaze layer is 30 pm.

[0057] The preparation method of the high-precision NTC thermistor comprises the following steps: S1: adding YCrO3 precursor powder into polysilazane, uniformly stirring, and ultrasonic dispersion to obtain a rare earth-based chromate slurry.

[0058] The molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5 in the preparation process of the precursor powder; the mass ratio of the precursor powder:polysilazane is 1:3 in the preparation process of the rare earth-based chromate slurry; and the particle size of the precursor powder is 3 μm.

[0059] S2: print the rare earth-based chromate slurry on the surface of the substrate layer 1, heat to 1550°C and sinter for 15 h to obtain a sensitive layer 2; after cooling; after cooling, spray the alumina sol on the surface of the sensitive layer 2, heat to 1100°C and anneal for 1 h to obtain an alumina sol layer 5; after cooling, spray the glass-ceramic glaze on the surface of the alumina sol layer 5, heat to 1200°C and anneal for 0.5 h to obtain a glass-ceramic glaze layer 6; after cooling, spray the alumina sol on the surface of the glass-ceramic glaze layer 6, heat to 1100°C and anneal for 1 h, cool, and obtain a high-precision NTC thermistor by attaching a silver-palladium electrode and a platinum wire lead;

[0060] The thickness of the sensitive layer is 20 μm; the thickness of the protective layer is 25 μm; the thickness of the alumina sol layer is 15 μm; and the thickness of the glass-ceramic glaze layer is 30 μm.

[0061] Comparative Example 5: a preparation method of a high-precision NTC thermistor, comprising the following steps: S1: add La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Cr2O3 into a ball mill tank, take ethanol as a dispersant, ball mill for 8 h to obtain a slurry; place the slurry in a vacuum drying oven at 100°C, grind, heat to 1100°C and pre-sinter for 5 h, grind, and obtain a precursor powder; add the precursor powder into polysilazane, stir uniformly, and ultrasonic dispersion to obtain a rare earth-based chromate slurry.

[0062] The molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5 in the preparation process of the precursor powder; the mass ratio of the precursor powder:polysilazane is 1:3 in the preparation process of the rare earth-based chromate slurry; and the particle size of the precursor powder is 3 μm.

[0063] S2: add chromium oxide into polysilazane, stir uniformly, and ultrasonic dispersion to obtain a chromium oxide slurry.

[0064] The mass ratio of chromium oxide:polysilazane is 1:1.5 in the preparation process of the chromium oxide slurry; and the particle size of the chromium oxide is 1 μm.

[0065] S3: printing the rare earth-based chromate slurry on the surface of the substrate layer 1, sintering at 1550 DEG C for 15h, obtaining the sensitive layer 2; after cooling, printing the chromium oxide slurry on the surface of the sensitive layer 2, annealing at 1300 DEG C for 1h, obtaining the protective layer 3; after cooling, attaching the silver-palladium electrode and the platinum wire lead, obtaining the high-precision NTC thermistor;

[0066] The thickness of the sensitive layer is 20 microns; and the thickness of the protective layer is 25 microns.

[0067] Experiment: resistance drift test: the electrode aging test is carried out in a high-temperature tube furnace, and the temperature is set to 1300 DEG C; during the aging process, the resistance drift rate of the sample with time is monitored until the aging time reaches 1000 hours, and finally the resistance drift data of the material after 1000 hours at 1300 DEG C is obtained;

[0068] Adhesion test: the scratch test is carried out by a scratch tester, the load is gradually applied, the friction force and acoustic emission signals are recorded, and the critical load of the coating is determined, so as to evaluate the adhesion strength of the film and the substrate after 1300 DEG C annealing.

[0069] The experimental data are shown in Table 1.

[0070] Table 1: Performance test data table of high-precision NTC thermistor

[0071] Resistance drift rate / % Adhesion strength / N Example 1 4.12(1300℃) 39.6 Example 2 3.99(1300℃) 41.2 Comparative Example 1 70(1000℃) / Comparative Example 2 20(1000℃) / Comparative Example 3 40(1000℃) / Comparative Example 4 6.78(1300℃) 16.9 Comparative Example 5 7.12(1300℃) 36.2

[0072] Conclusion: The NTC thermistor prepared by the method can work for a long time in a 1300 DEG C high-temperature environment, greatly expanding the application range of the NTC thermistor.

[0073] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, but that the application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered as exemplary and not limiting, and the scope of the application is defined by the appended claims and not by the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be embraced by the application. Any reference signs in the claims should not be considered as limiting the claims involved.

Claims

1. A high-precision NTC thermistor, characterized by: The NTC thermistor is sequentially composed of a substrate layer (1), a sensitive layer (2), a protective layer (3), and a sandwich protective layer (4) from bottom to top; the substrate layer (1) is alumina; the sensitive layer (2) is prepared by printing a rare earth-based chromate slurry; the protective layer (3) is prepared by printing a chromium oxide slurry; and the sandwich protective layer (4) is composed of two alumina sol layers (5) sandwiching a glass-ceramic glaze layer (6). The preparation method of the rare earth-based chromate slurry comprises the following steps: La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Cr2O3 are added into a ball mill tank, ethanol is used as a dispersant, and ball milling is performed for 8-10 h to obtain a slurry; the slurry is vacuum dried at 100-105 DEG C, ground, heated to 1100-1105 DEG C for pre-sintering for 5-5.5 h, and ground to obtain a precursor powder; the precursor powder is added into polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a rare earth-based chromate slurry.

2. The high-precision NTC thermistor according to claim 1, characterized in that: In the preparation process of the precursor powder, the molar ratio of La:Nd:Sm:Eu:Gd:Cr is 1:1:1:1:1:5; in the preparation process of the rare earth-based chromate slurry, the mass ratio of the precursor powder:polysilazane is (1-2):(3-4); and the particle size of the precursor powder is 3-5 μm.

3. The high-precision NTC thermistor according to claim 1, characterized in that: The preparation method of the chromium oxide slurry comprises the following steps: Chromium oxide is added into polysilazane, stirred uniformly, and ultrasonically dispersed to obtain a chromium oxide slurry.

4. The high-precision NTC thermistor according to claim 3, characterized in that: In the preparation process of the chromium oxide slurry, the mass ratio of chromium oxide:polysilazane is 1:(1.5-2); and the particle size of the chromium oxide is 1-1.5 μm.

5. The high-precision NTC thermistor according to claim 1, characterized in that: The thickness of the sensitive layer (2) is 20-25 μm; the thickness of the protective layer (3) is 20-25 μm; the thickness of the sandwich protective layer (4) is 60 μm; the thickness of the alumina sol layer (5) is 15-20 μm; and the thickness of the glass-ceramic glaze layer (6) is 20-30 μm.

6. The method according to any one of claims 1-5, characterized in that: The method comprises the following steps: The rare earth-based chromate slurry is printed on the surface of the substrate layer (1), heated to 1550-1555 DEG C for sintering for 15-16 h to obtain the sensitive layer (2); after cooling, the chromium oxide slurry is printed on the surface of the sensitive layer (2), heated to 1300-1305 DEG C for annealing for 1-1.5 h to obtain the protective layer (3); after cooling, the alumina sol is sprayed on the surface of the protective layer (3), heated to 1100-1105 DEG C for annealing for 1-1.5 h to obtain the alumina sol layer (5); after cooling, the glass-ceramic glaze is sprayed on the surface of the alumina sol layer (5), heated to 1200-1205 DEG C for annealing for 0.5-1 h to obtain the glass-ceramic glaze layer (6); after cooling, the alumina sol is sprayed on the surface of the glass-ceramic glaze layer (6), heated to 1100-1105 DEG C for annealing for 1-1.5 h, and cooled to obtain a high-precision NTC thermistor by attaching a silver-palladium electrode and a platinum wire lead.

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