A rare earth yttria, ceria doped high temperature negative temperature coefficient thermistor material and a preparation method thereof

Abstract

The application discloses a rare earth yttrium oxide and cerium oxide doped high-temperature negative temperature coefficient thermistor material and a preparation method thereof, and relates to the technical field of resistor devices.The thermistor material is composed of a thermistor material of trimanganese tetroxide, diiron trioxide, aluminum trioxide, silicon dioxide, diyttrium trioxide and cerium dioxide;the molar ratio of manganese, iron, aluminum, silicon, yttrium and cerium in the trimanganese tetroxide, diiron trioxide, aluminum trioxide, silicon dioxide, diyttrium trioxide and cerium dioxide is 0.4-0.8:0.3-0.5:0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5;the application can realize stable negative temperature coefficient characteristics in a wide temperature range of 25 DEG C-900 DEG C, greatly improves the stability and reliability of long-term use at high temperature, reduces the resistance value drift risk, guarantees the uniformity of raw material mixing through step-by-step grinding and calcination, and improves the density of the ceramic material through the parameter matching of cold isostatic pressing and high-temperature sintering, so that the air holes and structural defects are reduced.

Description

Technical Field

[0001] This invention belongs to the field of resistive device technology, specifically relating to a high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide, and its preparation method. Background Technology

[0002] Negative temperature coefficient (NTC) thermistors are thermistor materials whose resistivity decreases as temperature increases. They are characterized by high sensitivity, fast response, and small size. NTC thermistor ceramic materials are the core of thermistors. Industrial development and market demand have driven the application of high-temperature NTC thermistor materials, especially in the automotive field. The development of NTC thermistor materials from low temperature and room temperature to high temperature has become a necessity for industrial development. Therefore, the research and development of NTC thermistor ceramic materials for high-temperature applications is of great significance. Currently, platinum resistance temperature detectors are mainly used for high-temperature detection both domestically and internationally. Platinum resistance temperature detectors are used to measure temperatures below 600℃, and are mainly concentrated on thin and thick platinum films, that is, film-type resistance temperature detectors with a thin film on a ceramic material. Their maximum measurement temperature can reach 850℃. Platinum film resistance temperature sensors rely on the linearity of resistance and temperature to achieve temperature measurement. Below 500℃, it can be fully linearized. However, due to the inherent limitations of platinum metal, the linearity of the resistance-temperature relationship is unstable at high temperatures above 500℃. In addition, to improve sensitivity, the element size needs to be increased, which makes the sensor response time increase with the increase of size, making it difficult to improve performance. Currently, traditional thermistor materials include Mn-Co-Ni-Fe-O spinel-type thermistors, which are only suitable for temperatures below 300℃ and cannot meet the application requirements of high-temperature detection. Therefore, we propose a high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide and its preparation method to solve the above-mentioned problems, enabling it to work stably in a wide temperature range of 25-900℃ and possess both high sensitivity and structural stability. Summary of the Invention

[0003] The purpose of this invention is to provide a high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide, and its preparation method, which can operate stably in a wide temperature range of 25-900℃ and has both high sensitivity and structural stability, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide is composed of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide. The chemical composition of the thermistor material is xMnFeO3-(1-x)AlSiO3(YCe)4O 12 Where 0 ≤ x ≤ 0.7; The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.4-0.8:0.3-0.5:0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5.

[0005] Preferably, the thermistor material is prepared by mixing and grinding, pre-firing, re-mixing and grinding, molding, high-temperature sintering and electrode coating of the raw materials according to the molar ratio of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide in the composition by mass of 0.6:0.4:0.4:0.06:0.35:0.35.

[0006] Preferably, the thermistor material constant is B. 25 ℃ / 800 ℃ = 4467K - 9324K, resistivity at 25℃ is 1.74 × 10⁻⁶ 5 Ω.cm—2.17×10 8 Ω.cm.

[0007] Based on the above description of a rare-earth yttrium oxide and cerium oxide-doped high-temperature negative temperature coefficient thermistor material, this invention also provides a method for preparing the high-temperature negative temperature coefficient thermistor material, comprising the following steps: S1. MnFeO3 powder and AlSiO3(YCe)4 powder were prepared using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide as raw materials, respectively. S2. MnFeO3 powder and AlSiO3(YCe)4 powder are calcined and then refracted to obtain calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder, respectively. S3. Mix MnFeO3 calcined powder and AlSiO3(YCe)4 calcined powder in a ratio of x:(1-x), where x is 0-0.7. After mixing, grind for 4-8 hours to obtain composite powder. S4. The composite powder is cold isostatically pressed and sintered at high temperature to obtain a high-temperature thermistor ceramic material. S5. Platinum paste electrodes are coated on both sides of the high-temperature thermistor ceramic material and sintered to obtain a high-temperature negative temperature coefficient thermistor material.

[0008] Preferably, the MnFeO3 powder is prepared by first mixing manganese tetroxide and ferric oxide at a manganese to iron molar ratio of 0.4-0.8:0.3-0.5, and then grinding the mixed raw materials in agate for 4-8 hours.

[0009] Preferably, the AlSiO3(YCe)4 powder is prepared by first mixing aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide in a molar ratio of aluminum, silicon, yttrium and cerium of 0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5, and then grinding the mixed raw materials in agate for 4-8 hours.

[0010] Preferably, in step S2, the calcination conditions are: calcination temperature of 800-1000℃, calcination time of 5-8 hours, and re-grinding time of 5-8 hours.

[0011] Preferably, in step S4, cold isostatic pressing is performed at a pressure of 10-25 kg / cm². 2 The blocks are pressed into blocks under pressure for 1-3 minutes. The blocks are then subjected to cold isostatic pressing at a pressure of 300-350 MPa for 2-4 minutes, and then sintered at a temperature of 1300-1600℃ for 6-12 hours.

[0012] Preferably, in step S5, the conditions for sintering the platinum paste electrode are: sintering temperature of 900-1000℃, sintering time of constant temperature sintering for 30 minutes, and cooling to room temperature with the furnace after sintering.

[0013] Preferably, after coating the platinum paste electrode, it needs to be dried at a temperature of 100-120℃ for 1-2 hours before high-temperature sintering.

[0014] The present invention proposes a high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide, and its preparation method thereof, which has the following advantages compared with the prior art: 1. This invention utilizes a thermistor material composed of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide to achieve a stable negative temperature coefficient over a wide temperature range of 25℃-900℃, significantly improving the stability and reliability of long-term high-temperature use and reducing the risk of resistance drift. 2. This invention ensures the uniformity of raw material mixing through stepwise grinding and calcination. The combination of parameters for cold isostatic pressing and high-temperature sintering improves the density of ceramic materials and reduces porosity and structural defects. Meanwhile, cerium oxide, as a sintering aid, can reduce the sintering temperature required in this preparation process and optimize production energy consumption. The process of coating the platinum paste electrode ensures the stability of the material electrode contact and ensures consistent electrical performance output. 3. The thermistor material prepared by this invention has the inherent advantages of high sensitivity and fast response of NTC materials, as well as high temperature stability. Moreover, the preparation process is easy to industrialize and mass-produce, and the raw materials are conventional metal oxides, so the cost is controllable. Attached Figure Description

[0015] Figure 1 A flowchart illustrating the preparation process of high-temperature negative temperature coefficient thermistor material according to an embodiment of the present invention is shown; Figure 2 SEM images of a Y, Ce co-doped perovskite-like system according to Embodiment 1 of the present invention, which was kept at 1600°C for 4 hours, are shown. Figure 3 The resistance-temperature characteristic curves of rare earth yttrium oxide and cerium oxide doped high-temperature NTC thermistor materials according to embodiments of the present invention are shown. Figure 4 The X-ray diffraction pattern of a rare earth Y2O3 and CeO2 co-doped thermistor ceramic material according to an embodiment of the present invention is shown. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] This invention provides, for example Figure 1 The above describes a high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide. This thermistor material is composed of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide. The chemical composition of the thermistor material is xMnFeO3-(1-x)AlSiO3(YCe)4O 12 Where 0 ≤ x ≤ 0.7; The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the aforementioned manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.4-0.8:0.3-0.5:0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5; the material constant of the thermistor is B. 25 ℃ / 800 ℃ = 4467K - 9324K, resistivity at 25℃ is 1.74 × 10⁻⁶ 5 Ω.cm—2.17×10 8 Ω.cm.

[0018] Based on the above description of a rare-earth yttrium oxide and cerium oxide-doped high-temperature negative temperature coefficient thermistor material, this invention also provides a method for preparing the high-temperature negative temperature coefficient thermistor material, comprising the following steps: S1. MnFeO3 powder and AlSiO3(YCe)4 powder were prepared using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide as raw materials, respectively. The MnFeO3 powder is prepared by first mixing manganese tetroxide and ferric oxide at a manganese to iron molar ratio of 0.4-0.8:0.3-0.5, and then grinding the mixed raw material in agate for 4-8 hours. The AlSiO3(YCe)4 powder is prepared by first mixing aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide in a molar ratio of aluminum, silicon, yttrium and cerium of 0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5, and then grinding the mixed raw materials in agate for 4-8 hours. S2. MnFeO3 powder and AlSiO3(YCe)4 powder were calcined and refmilled to obtain calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder, respectively. The calcination conditions were: calcination temperature of 800-1000℃, calcination time of 5-8 hours, and refmilling time of 5-8 hours. S3. Mix MnFeO3 calcined powder and AlSiO3(YCe)4 calcined powder in a ratio of x:(1-x), where x is 0-0.7. After mixing, grind for 4-8 hours to obtain composite powder. S4. The composite powder is cold isostatically pressed and then sintered at high temperature to obtain a high-temperature thermistor ceramic material; specifically, the cold isostatic pressing is performed at a pressure of 10-25 kg / cm³. 2 The blocks are pressed into blocks under pressure for 1-3 minutes. The blocks are then subjected to cold isostatic pressing at a pressure of 300-350 MPa for 2-4 minutes, and then sintered at a temperature of 1300-1600℃ for 6-12 hours.

[0019] S5. Coat platinum paste electrodes on both sides of the high-temperature thermistor ceramic material and sinter to obtain a high-temperature negative temperature coefficient thermistor material. After coating the platinum paste electrodes, they need to be dried at a temperature of 100-120℃ for 1-2 hours before high-temperature sintering. The sintering conditions for the platinum paste electrodes are: sintering temperature of 900-1000℃, sintering time of constant temperature sintering for 30 minutes, and cooling to room temperature with the furnace after sintering.

[0020] To verify the performance of the high-temperature negative temperature coefficient thermistor material prepared by the above-described method, the following examples and comparative examples are provided:

[0021] Example 1

[0022] A method for preparing a high-temperature negative temperature coefficient thermistor material involves using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide as raw materials to prepare MnFeO3 powder and AlSiO3(YCe)4 powder, respectively. The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.5:0.3:0.3:0.05:0.2:0.2. The MnFeO3 powder and AlSiO3(YCe)4 powder are then compared. MnFeO3 (YCe)4 powder was ground separately for 8 hours. MnFeO3 powder and AlSiO3 (YCe)4 powder were calcined at 950℃ for 6 hours, then ground separately for 7 hours to obtain calcined MnFeO3 powder and calcined AlSiO3 (YCe)4 powder. The calcined MnFeO3 powder and AlSiO3 (YCe)4 powder were then mixed at a ratio of 0.5:(1-0.5) and ground for another 7 hours to obtain a composite powder. The composite powder was then weighed at 25 kg / cm³. 2 The high-temperature negative temperature coefficient thermistor material is obtained by pressing the material under pressure for 2 minutes, cold isostatic pressing, holding the pressure at 350 MPa for 2 minutes, and then sintering at 1450℃ for 10 hours. Platinum paste electrodes are coated on both sides of the high-temperature thermistor material and sintered at 1000℃ for 30 minutes.

[0023] Example 2

[0024] A method for preparing a high-temperature negative temperature coefficient thermistor material involves using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide as raw materials to prepare MnFeO3 powder and AlSiO3(YCe)4 powder, respectively. The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.6:0.4:0.4:0.06:0.35:0.35. The MnFeO3 powder and AlSiO3(YCe)4 powder are then compared. MnFeO3 (YCe)4 powder was ground separately for 7 hours. MnFeO3 powder and AlSiO3 (YCe)4 powder were calcined at 1000℃ for 7 hours, then ground separately for 8 hours to obtain calcined MnFeO3 powder and calcined AlSiO3 (YCe)4 powder. The calcined MnFeO3 powder and AlSiO3 (YCe)4 powder were then mixed at a ratio of 0.6:(1-0.6) and ground for another 8 hours to obtain a composite powder. The composite powder was then subjected to a process with a density of 25 kg / cm³. 2 The material is pressed into blocks under pressure for 3 minutes, then subjected to cold isostatic pressing at 300 MPa for 2 minutes, followed by sintering at 1500℃ for 8 hours. Platinum paste electrodes are then coated onto both sides of the high-temperature thermistor ceramic material and sintered at 950℃ for 30 minutes to obtain a high-temperature negative temperature coefficient thermistor material. Figure 3 As shown, the resistance-temperature characteristic curves of rare earth yttrium oxide and cerium oxide-doped high-temperature NTC thermistor materials are plotted in the temperature range of 25℃-900℃, with temperature as the abscissa and resistivity as the ordinate. The curves show a continuous monotonically decreasing trend with no inflection point, no plateau, and no rebound, proving that the material maintains a stable negative temperature coefficient (NTC) characteristic across the entire temperature range of 25℃-900℃. Moreover, the resistivity decreases smoothly with increasing temperature without abrupt changes, indicating that the crystal structure is stable, without crystal transformation, phase transition, or high-temperature decomposition. The curve slope is moderate, corresponding to a B value of 4467K~9324K, demonstrating high sensitivity and meeting the requirements for high-temperature measurement.

[0025] Example 3

[0026] A method for preparing a high-temperature negative temperature coefficient thermistor material involves using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide as raw materials to prepare MnFeO3 powder and AlSiO3(YCe)4 powder, respectively. The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.7:0.5:0.35:0.08:0.5:0.5. The MnFeO3 powder and AlSiO3(YCe)4 powder are then compared. MnFeO3 (YCe)4 powder was ground separately for 6 hours. MnFeO3 powder and AlSiO3 (YCe)4 powder were calcined at 900℃ for 6 hours, then ground separately for 7 hours to obtain calcined MnFeO3 powder and calcined AlSiO3 (YCe)4 powder. The calcined MnFeO3 powder and AlSiO3 (YCe)4 powder were then mixed at a ratio of 0.7:(1-0.7) and ground for another 8 hours to obtain a composite powder. The composite powder was then weighed at 25 kg / cm³. 2 The material is pressed into blocks under pressure for 2 minutes, then subjected to cold isostatic pressing at 350 MPa for 3 minutes, followed by sintering at 1600℃ for 6 hours. Platinum paste electrodes are then coated onto both sides of the high-temperature thermistor ceramic material and sintered at 900℃ for 30 minutes to obtain a high-temperature negative temperature coefficient thermistor material. Figure 2 The image shows the SEM of the Y and Ce co-doped perovskite-like system after being kept at 1600℃ for 4 hours. The overall microstructure shows that the material has a dense polycrystalline ceramic structure with regular polygonal grains of uniform size (no obvious coarse grains or fine microcrystals). The grain boundaries are clear and continuous. There are no obvious pores, microcracks or impurity phases at the grain boundaries, and the material has high density. Under high magnification, white / black spots without elemental segregation can be observed at the grain boundaries. Y and Ce elements are uniformly distributed in the grains and grain boundaries.

[0027] like Figure 4 The figure shows the X-ray diffraction pattern of rare earth Y₂O₃ and CeO₂ co-doped thermistor ceramic material. The horizontal axis represents 2θ (°), and the vertical axis represents the diffraction peak intensity. In the figure, the main peak is related to the perovskite-like structure (AlSiO₃(YCe)₄O₂). 12 The diffraction peaks match the MnFeO3 perovskite phase standard card, showing no impurity peaks, no second phase, and no residual rare earth oxide peaks. The sharp peak shapes and narrow half-maximum widths (HWHM) indicate high crystallinity, well-developed and uniform grain size. The absence of Y2O3 and CeO2 primary oxide diffraction peaks indicates that Y2O3 is not present in the diffraction peaks. 3+ Ce 4+ Completely entering the crystal lattice to form a solid solution, achieving homogeneous doping. Compared with undoped / single-doped samples, co-doping does not change the main crystal phase structure, but only optimizes the lattice stability and density.

[0028] Example 4

[0029] A method for preparing a high-temperature negative temperature coefficient thermistor material involves using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide as raw materials to prepare MnFeO3 powder and AlSiO3(YCe)4 powder, respectively. The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.4:0.3:0.3:0.05:0.2:0.2. The MnFeO3 powder and AlSiO3 powder... (YCe)4 powder was ground separately for 8 hours. MnFeO3 powder and AlSiO3(YCe)4 powder were calcined at 1000℃ for 7 hours, then ground separately for another 7 hours to obtain calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder. The calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder were then mixed at a ratio of 0.4:(1-0.4) and ground for another 6 hours to obtain a composite powder. The composite powder was then weighed at 20 kg / cm³. 2 The high-temperature negative temperature coefficient thermistor material is obtained by pressing the material under pressure for 3 minutes, cold isostatic pressing, holding the pressure at 300 MPa for 2 minutes, and then sintering at 1650℃ for 8 hours. Platinum paste electrodes are coated on both sides of the high-temperature thermistor material and sintered at 1000℃ for 30 minutes.

[0030] Example 5

[0031] A method for preparing a high-temperature negative temperature coefficient thermistor material involves using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide as raw materials to prepare MnFeO3 powder and AlSiO3(YCe)4 powder, respectively. The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.6:0.4:0.4:0.07:0.4:0.4. The MnFeO3 powder and AlSiO3 powder... (YCe)4 powder was ground separately for 7 hours. MnFeO3 powder and AlSiO3(YCe)4 powder were calcined at 980℃ for 7 hours, then ground separately for another 7 hours to obtain calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder. The calcined MnFeO3 powder and AlSiO3(YCe)4 powder were then mixed at a ratio of 0.55:(1-0.55) and ground for another 7 hours to obtain a composite powder. The composite powder was then weighed at 22 kg / cm³. 2The high-temperature negative temperature coefficient thermistor material is obtained by pressing the material under pressure for 2 minutes, cold isostatic pressing, holding the pressure at 320 MPa for 3 minutes, and then sintering at 1550℃ for 9 hours. Platinum paste electrodes are coated on both sides of the high-temperature thermistor material and sintered at 980℃ for 30 minutes.

[0032] Comparative Example 1 The preparation process is completely consistent with that of Example 2. The difference is that the raw material ratio is: the molar ratio of manganese tetroxide, ferric oxide, aluminum oxide and silicon dioxide is 0.6:0.4:0.4:0.06. Yttrium oxide and cerium dioxide are not present. The value of x in the chemical composition is 0.6.

[0033] Comparative Example 2 The preparation process is completely consistent with that of Example 2. The difference is that the raw material ratio is: manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, and yttrium in which the molar ratio of manganese, iron, aluminum, silicon and yttrium is 0.6:0.4:0.4:0.06:0.7. Yttrium and cerium dioxide are not included. The value of x in the chemical composition is 0.6.

[0034] Comparative Example 3 The preparation process is completely consistent with that of Example 2. The difference is that the raw material ratio is: manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, and cerium dioxide. The molar ratio of manganese, iron, aluminum, silicon, and cerium is 0.6:0.4:0.4:0.06:0.7. Yttrium oxide and cerium dioxide are not included. The value of x in the chemical composition is 0.6.

[0035] Comparative Example 4 The preparation process is exactly the same as in Example 2. The difference is that the value of x in the chemical composition is 0.8.

[0036] Comparative Example 5 Using manganese tetroxide, cobalt tetroxide, nickel oxide, and ferric oxide as raw materials, they were mixed in a molar ratio of manganese, cobalt, nickel, and iron of 2:1:1:1. The mixture was then thoroughly ground in an agate mortar for 8 hours to obtain a uniform mixed oxide powder. This powder was placed in an alumina crucible and then placed in a muffle furnace. The temperature was increased to 900℃ at a rate of 5℃ / min, and calcined at this temperature for 6 hours to achieve initial crystal formation. The calcined powder was then removed, cooled to room temperature, and ground again in an agate mortar for 8 hours to refine the grains and ensure powder uniformity, yielding a spinel-type precursor powder. This precursor powder was then loaded into a mold and ground at 25 kg / cm³. 2Dry pressing is performed under pressure for 1 minute to obtain a shaped blank. The shaped blank is then subjected to cold isostatic pressing at a pressure of 300 MPa for 2 minutes to increase the density of the blank and reduce internal porosity. The cold isostatically pressed blank is placed in an alumina crucible and then placed in a high-temperature sintering furnace. The temperature is increased to 1200℃ at a heating rate of 5℃ / min and sintered at a constant temperature for 8 hours. The blank is then cooled to room temperature with the furnace to obtain a traditional spinel-type Mn-Co-Ni-Fe-O ceramic substrate. High-purity platinum paste electrodes are uniformly coated on both sides of the ceramic substrate. The substrate is then placed in a muffle furnace and heated to 950℃ for 30 minutes to complete the electrode firing, thus obtaining a traditional spinel-type Mn-Co-Ni-Fe-O thermistor material.

[0037] The thermistor materials prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to tests for their resistance-temperature characteristics, long-term high-temperature stability, effectiveness of NTC characteristics, and density. The test methods were as follows: Resistance-temperature characteristics: The resistivity of the material is tested using a high-temperature resistance testing system within the range of 25℃-900℃, and the material constant B is calculated. 25 ℃ / 800 ℃, where B value = ln(R) 25 / R 800 ) / (1 / 298.15-1 / 1073.15), where R is the resistivity at the corresponding temperature; High temperature long-term stability: The samples were aged in constant temperature ovens at 300℃, 500℃ and 800℃ for 1000h respectively. The resistivity at 25℃ before and after aging was tested, and the absolute value of the resistance deviation was calculated (|(Rafter-Rbefore) / Rbefore|×100%). NTC characteristic validity: Determine whether the resistivity in the range of 25℃-900℃ continuously decreases with increasing temperature. If it continuously decreases, it has effective NTC characteristics; otherwise, it does not have effective NTC characteristics. The test results are shown in Table 1 below: (In Table 1, resistance deviation A is the resistance deviation of the 300℃ aging test, resistance deviation B is the resistance deviation of the 500℃ aging test, and resistance deviation C is the resistance deviation of the 800℃ aging test.) Table 1

[0038] The following conclusions can be drawn from the data in Table 1: 1. Among Examples 1-5, Example 2 has the optimal raw material ratio and process parameters. Its B value is in the middle range of 4467K-9324K, its resistivity at 25℃ is moderate, and its high-temperature aging resistance deviation is the lowest among all examples, resulting in the best overall performance. Furthermore, the value of x in the chemical composition is positively correlated with the value of B: as x increases from 0.4 to 0.7, the value of B... 25 ℃ / 800As the temperature increases from 5321K to 9324K, the resistivity at 25℃ also increases exponentially with the increase of x, indicating that the B value and resistivity can be customized by adjusting the x value to meet the parameter requirements of different high-temperature detection scenarios. In the examples, all samples maintained effective NTC characteristics at temperatures ranging from 25℃ to 900℃, and the absolute value of the resistance deviation after aging at 800℃ for 1000h was ≤1.5%, indicating that within the range of raw material ratios and x values ​​provided by this invention, the materials all possess excellent high-temperature NTC characteristics and long-term stability. Fine-tuning of process parameters such as calcination temperature, sintering time, and cold isostatic pressing pressure within the range defined by this invention only slightly affects the material stability deviation value and does not change the core NTC characteristics, proving that the preparation process parameter range has good process tolerance and is suitable for industrial mass production.

[0039] 2. Comparing Examples 1-5 with Comparative Example 1 (without rare earth doping), it was found that without Y and Ce doping, the material's B value decreased significantly to 2154K, the thermal sensitivity decreased significantly, and the NTC characteristics failed after 700℃, which could not meet the high-temperature detection requirements of 900℃. Furthermore, the high-temperature aging resistance deviation of the material without rare earth doping is much higher than that of the example, reaching 15.6% after aging at 800℃. This indicates that the doping of rare earth Y and Ce is the core factor in improving the material's density, high-temperature stability, and wide-temperature NTC characteristics. Without these doping elements, the material cannot achieve stable operation at high temperatures.

[0040] 3. Comparing Examples 1-5 with Comparative Examples 2 (Y doping only) and 3 (Ce doping only), it was found that although materials doped with Y or Ce alone still have effective NTC characteristics at 900℃, their high-temperature aging deviation is much higher than that of the examples (e.g., aging deviations at 800℃ reach 7.5% and 6.8% respectively), proving that the effect of Y and Ce synergistic doping is far superior to single rare earth doping; the high-temperature aging deviation of materials doped with Y alone is slightly better than that of materials doped with Ce alone, reflecting the core role of Y2O3 in suppressing lattice defects and reducing resistance drift; In the embodiments, Y and Ce co-doping achieves the complementary effect of Ce increasing density and Y stabilizing the lattice, enabling the material to simultaneously possess high density, high sensitivity, and extremely low high-temperature aging deviation, demonstrating that the Y and Ce co-doping design in this invention can achieve high-temperature performance of the material.

[0041] 4. Comparing Examples 1-5 with Comparative Example 4 (x=0.8, out of range), it was found that when the value of x exceeded the upper limit of 0.7 specified in the patent, the NTC characteristics of the material failed after 800℃, and it could not reach the upper limit of 900℃. Its high-temperature aging deviation increased significantly, indicating that the value of x in the range of 0≤x≤0.7 is a necessary condition for the material to maintain effective NTC characteristics at 900℃. When it exceeds this range, the proportion of MnFeO3 is too high, which destroys the stability of the perovskite-like matrix structure and leads to a significant decrease in the high-temperature performance of the material.

[0042] 5. Comparison of Examples 1-5 with Comparative Example 5 (traditional spinel type) revealed that the traditional Mn-Co-Ni-Fe-O spinel type material loses its NTC characteristics after 300℃, failing to meet the requirements for medium- and high-temperature detection. In contrast, the material prepared by this invention can operate stably up to 900℃, achieving a breakthrough in the temperature range from 300℃ to 900℃. Even under aging conditions at 300℃, the resistance deviation of the traditional material reaches 2.8%, far exceeding that of the examples. This indicates that the design of the perovskite-like structure, AlSiO3 composite, and rare earth doping in this invention provides a qualitative improvement in high-temperature stability and thermosensitive properties compared to traditional spinel type materials, enabling its application in high-temperature fields.

[0043] In summary, the rare-earth Y and Ce co-doping, the raw material range of 0.4-0.8 molar ratio, the chemical composition of 0≤x≤0.7, and the perovskite-like matrix structure of this invention form an organic whole, and none of them can be omitted. This design enables the material to break through the temperature range limitation of traditional NTC thermistors, achieving effective NTC characteristics over a wide temperature range of 25℃-900℃. It also possesses high sensitivity, high density, and extremely low high-temperature aging deviation. At the same time, the preparation process parameters have good tolerance, and the raw materials are conventional oxides, making it suitable for industrial mass production. It can effectively replace platinum resistance thermometers in the field of high-temperature detection of 500℃-900℃, solving the problems of poor high-temperature linearity and the contradiction between sensitivity and response time of platinum resistance thermometers.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide, characterized in that: A thermistor material composed of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide, wherein the chemical composition of the thermistor material is xMnFeO3-(1-x)AlSiO3(YCe)4O 12 Where 0 ≤ x ≤ 0.7; The molar ratio of manganese, iron, aluminum, silicon, yttrium, and cerium in the manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide, and cerium dioxide is 0.4-0.8:0.3-0.5:0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.

5.

2. The high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide according to claim 1, characterized in that: The thermistor material is prepared by mixing and grinding, pre-firing, re-mixing and grinding, molding, high-temperature sintering and electrode coating of the raw materials according to the molar ratio of manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide in the above-mentioned materials, based on the mass composition of 0.6:0.4:0.4:0.06:0.35:0.

35.

3. The high-temperature negative temperature coefficient thermistor material doped with rare earth yttrium oxide and cerium oxide according to claim 2, characterized in that: The material constant of the thermistor is B. 25 ℃ / 800 ℃ = 4467K - 9324K, resistivity at 25℃ is 1.74 × 10⁻⁶ 5 Ω.cm—2.17×10 8 Ω.cm.

4. A method for preparing a high-temperature negative temperature coefficient thermistor material, comprising preparing a rare-earth yttrium oxide and cerium oxide doped high-temperature negative temperature coefficient thermistor material as described in any one of claims 1-2, characterized in that: Includes the following steps: S1. MnFeO3 powder and AlSiO3(YCe)4 powder were prepared using manganese tetroxide, ferric oxide, aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide as raw materials, respectively. S2. MnFeO3 powder and AlSiO3(YCe)4 powder were calcined and then refracted to obtain calcined MnFeO3 powder and calcined AlSiO3(YCe)4 powder, respectively. S3. Mix MnFeO3 calcined powder and AlSiO3(YCe)4 calcined powder in a ratio of x:(1-x), where x is 0-0.

7. After mixing, grind for 4-8 hours to obtain composite powder. S4. The composite powder is cold isostatically pressed and sintered at high temperature to obtain a high-temperature thermistor ceramic material. S5. Platinum paste electrodes are coated on both sides of the high-temperature thermistor ceramic material and sintered to obtain a high-temperature negative temperature coefficient thermistor material.

5. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 4, characterized in that: The MnFeO3 powder is prepared by first mixing manganese tetroxide and ferric oxide at a manganese to iron molar ratio of 0.4-0.8:0.3-0.5, and then grinding the mixed raw materials in agate for 4-8 hours.

6. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 5, characterized in that: The AlSiO3(YCe)4 powder is prepared by first mixing aluminum oxide, silicon dioxide, yttrium oxide and cerium dioxide in a molar ratio of aluminum, silicon, yttrium and cerium of 0.3-0.5:0.05-0.08:0.2-0.5:0.2-0.5, and then grinding the mixed raw materials in agate for 4-8 hours.

7. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 4, characterized in that: In step S2, the calcination conditions are: calcination temperature of 800-1000℃, calcination time of 5-8 hours, and re-grinding time of 5-8 hours.

8. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 4, characterized in that: In step S4, cold isostatic pressing is performed at a pressure of 10-25 kg / cm². 2 The blocks are pressed into blocks under pressure for 1-3 minutes. The blocks are then subjected to cold isostatic pressing at a pressure of 300-350 MPa for 2-4 minutes, and then sintered at a temperature of 1300-1600℃ for 6-12 hours.

9. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 4, characterized in that: In step S5, the conditions for sintering the platinum paste electrode are: sintering temperature of 900-1000℃, sintering time of 30 minutes at constant temperature, and cooling to room temperature with the furnace after sintering.

10. The method for preparing a high-temperature negative temperature coefficient thermistor material according to claim 9, characterized in that: After coating the platinum paste electrode, it needs to be dried at 100-120℃ for 1-2 hours before high-temperature sintering.

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