PTC (Positive Temperature Coefficient) thermosensitive resistor for low-power-consumption variable-frequency starting and preparation method of PTC thermosensitive resistor

Abstract

The invention discloses a low-power-consumption variable-frequency starting PTC (Positive Temperature Coefficient) thermistor and a preparation method thereof, and belongs to the technical field of PTC thermistors. The resistor comprises a PTC ceramic base material, a glass phase material, a semiconducting agent and a manganese additive, wherein the high-temperature-resistant ceramic material comprises the following raw materials in percentage by mass: 48%-62% of BaCO3, 22%-38% of TiO2, 0.5%-1.2% of SrCO3, 4%-8% of CaCO3, 4%-8% of PbO, 0.3%-0.6% of a glass phase material, 0.25%-0.45% of a semiconducting agent and 0.3%-0.6% of Mn (NO3) 2. Through the synergistic effect of component regulation, dual coating modification and segmented atmosphere sintering, a grain boundary structure and a potential barrier are effectively regulated, the contradiction between size reduction and reliability, between Curie temperature reduction and recovery time, and between chip temperature rise and thermal shock resistance is solved, and high reliability and excellent performance of a product under low power consumption are achieved.

Description

Technical Field

[0001] This application belongs to the field of PTC thermistor technology, specifically relating to a low-power PTC thermistor for frequency conversion starting and its preparation method. Background Technology

[0002] Currently, traditional PTC thermistors widely used in the starting of refrigerator and freezer compressors still have significant bottlenecks in terms of power consumption and reliability. Taking a typical product as an example, its chip size is φ15.8*t2.5mm, its Curie temperature (Tc25) is 135±7℃, its room temperature resistance (R25) is 15Ω±20%, and its power consumption is generally as high as 2.6W~2.8W, with a breakdown voltage level typically around 700V. Such performance indicators are no longer sufficient to meet the stringent standards of modern variable frequency refrigeration equipment for core components: "low energy consumption, high voltage resistance, and long lifespan."

[0003] The power consumption of PTC thermistors is influenced by many factors, primarily including chip size, Curie temperature, and assembly structure. However, optimizing these factors using traditional manufacturing techniques often involves irreconcilable technical contradictions. For example, it is impossible to reduce product size without compromising reliability; it is impossible to lower Curie temperature without increasing recovery time; and it is impossible to increase chip temperature rise without compromising the chip's thermal shock resistance. Summary of the Invention

[0004] The purpose of this application is to provide a low-power variable frequency starter PTC thermistor and its preparation method. By introducing a high-efficiency glass phase material and manganese additives through a five-element main formulation system to regulate grain growth, and establishing a synergistic effect between different processes, a synergistic improvement in low power consumption and high reliability is achieved.

[0005] To achieve the above objectives, this application provides a low-power PTC thermistor for frequency conversion starting, comprising a PTC ceramic matrix, a glass phase material, a semiconductor agent, and a manganese additive; wherein, by mass percentage, it comprises the following raw materials: BaCO3: 48%~62%, TiO2: 22%~38%, SrCO3: 0.5%~1.2%, CaCO3: 4%~8%, PbO: 4%~8%, glass phase material: 0.3%~0.6%, semiconductor agent: 0.25%~0.45%, Mn(NO3)2: 0.3%~0.6%; wherein, The glass phase material includes at least one selected from TiO2, SiO2, Al2O3, Li2CO3, and BN; the semiconductor agent includes at least one selected from Nb2O5, Sm2O3, and Er2O3; wherein... The low-power variable frequency starter PTC thermistor has a power consumption of <2.2W, a static withstand voltage of >900V, and a dynamic withstand voltage of >500V.

[0006] Preferably, the glass phase material is SiO2.

[0007] Preferably, the semiconductor agent comprises equal masses of Sm2O3 and Er2O3.

[0008] Furthermore, the formulation of the PTC ceramic matrix is ​​(Ba 1-x-y-z Sr x Pb y Ca z TiO3, where x ranges from 1% to 5%, y ranges from 5% to 8%, z ranges from 12% to 22%, and the total amount of x + y + z does not exceed 35%.

[0009] This application also discloses a method for fabricating a low-power frequency conversion starting PTC thermistor, including the following steps: The semiconductor agent was mixed with nano-alumina powder and then coated and modified to obtain a coated semiconductor agent. After weighing the remaining raw materials, they are mixed with the coating semiconductor agent by wet ball milling and then dried to obtain ceramic material; The ceramic material is pre-calcined at 1160℃~1200℃ for 3.5h~4.5h, and then pulverized to obtain the pre-calcined material; Manganese nitrate, glass powder, and rare earth oxides were dispersed in ethanol to prepare a coating solution. The pre-calcined material was then coated with the coating solution and dried and heat-treated to obtain the modified pre-calcined material. The modified pre-calcined material is mixed with dispersant and defoamer to form a slurry. The slurry is mixed with binder and plasticizer and then subjected to spray granulation, tableting and calcination in sequence to obtain ceramic sheets. Nickel and silver layers were prepared on the surface of a ceramic sheet by sputtering and printing, respectively, to obtain a PTC thermistor for power consumption frequency conversion starting.

[0010] Furthermore, the thickness of the sputtered nickel layer is 0.4μm~0.6μm (sputtering parameters 1:4), and the thickness of the printed silver layer is 3.0μm~8.0μm (180 mesh screen, 80% silver paste).

[0011] Furthermore, in the wet ball milling process, the mass ratio of raw material, balls and water is 1:(1~1.5):(1~1.5), the ball milling frequency is 30Hz~50Hz, and the ball milling time is 30h~35h.

[0012] Furthermore, the dispersant includes at least one of ammonia, AKM and VT95, and the mass of the dispersant is 0.08% to 0.12% of the precalcined material.

[0013] Furthermore, the defoamer includes at least one of F-102, n-octanol and JH-818, and the mass of the defoamer is 0.002% to 0.003% of the precalcined material.

[0014] Furthermore, the rotation speed of the mixed abrasive is 1100 rpm to 1300 rpm, and the time is 20 min to 40 min.

[0015] Furthermore, the adhesive includes at least one of PVA, PVB, and PTN10M, and the mass of the adhesive is 15% to 18% of the slurry.

[0016] Furthermore, the plasticizer includes at least one of S9002, LU-6418 and diethylene glycol, and the mass of the plasticizer is 0.6% to 1.2% of the slurry.

[0017] Furthermore, the semiconductor agent is coated and modified by mixing it with nano-alumina powder, including: mixing the semiconductor agent with 0.05wt%~0.08wt% of nano-alumina powder, and treating it by air jet mill at a speed of 25000rpm~30000rpm for 12min~18min.

[0018] Furthermore, the concentration of manganese nitrate in the coating solution is 0.1wt%~0.3wt%, the concentration of glass powder is 0.05wt%~0.15wt%, and the concentration of rare earth oxides is 0.02wt%~0.08wt%. The drying heat treatment includes drying the coated powder at 80℃~120℃, and then heat-treating it at 600℃~800℃ for 1h~2h.

[0019] Furthermore, the calcination treatment includes the following steps: Heat to 600℃~700℃ at a rate of 2℃ / min~3℃ / min, and hold for 60min~90min; Introduce a nitrogen-oxygen mixed atmosphere with an oxygen content of 1% to 5%, and raise the temperature to 1150℃ to 1250℃ at a rate of 4℃ / min to 5℃ / min, and hold for 30min to 60min. Switch to pure oxygen or air with an oxygen content of 10%~21%, and heat to a peak temperature of 1320℃~1350℃ at a rate of 3℃ / min~4℃ / min, and hold for 30min~50min. Cool to 900°C at a rate of 3°C / min to 5°C / min, and then cool to room temperature in the furnace.

[0020] Furthermore, the thickness of the nickel layer is 0.4 μm to 0.6 μm, and the thickness of the silver layer is 3 μm to 8 μm.

[0021] In summary, this application has the following advantages: The formulation system developed in this application is a novel PTC ceramic material formulation system with multiple donor doping, high donor and acceptor doping, Sr-Pb co-addition, and CaCO3 refiner, which improves the ceramic material structure at the microscopic level and achieves synergistic improvement in performance and reliability.

[0022] Specifically, this application first optimizes the donor ion combination and doping ratio to precisely control the semiconductivity of the ceramic material, ensuring good conductivity while avoiding performance fluctuations caused by single doping, providing ionic-level support for improving the temperature coefficient and resistance ratio. Secondly, by leveraging the inhibitory effect of Sr on grain growth and the ability of Pb to regulate the Curie temperature, the dual goals of grain refinement and temperature characteristic optimization are achieved, reducing local electric field concentration caused by grain inhomogeneity and lowering voltage effects. Finally, the introduction of CaCO3 as a grain refiner further promotes grain homogenization, improves the compactness of the ceramic material's microstructure, and reduces internal voids and defects. This not only improves the ceramic material's voltage withstand capability but also enhances the chip's shock resistance, ensuring reliability from a structural perspective.

[0023] Through the formulation system of this application, the temperature coefficient of the ceramic material is significantly improved, the sensitivity to temperature changes is enhanced, and it can quickly respond to temperature fluctuations in the operating condition to achieve sudden changes in resistance; the resistance ratio is greatly improved, and the suppression effect on compressor starting current is better; the voltage resistance level is significantly improved, adapting to complex voltage environments, while effectively reducing product power consumption, thereby achieving a technological breakthrough in performance improvement, power consumption reduction and reliability enhancement. Attached Figure Description

[0024] Figure 1 This is a schematic diagram comparing the grain structures of Comparative Example 1 and Example 1 of this application, wherein, Figure 1 (a) in the figure shows the grain structure of Comparative Example 1. Figure 1 (b) in the figure represents the grain structure of Example 1.

[0025] Figure 2 This is a schematic diagram comparing the grain structures of Comparative Example 2 and Example 1 of this application, wherein, Figure 2 (a) in the figure shows the grain structure of Comparative Example 2. Figure 2 (b) in the figure represents the grain structure of Example 1.

[0026] Figure 3 This is a schematic diagram comparing the grain structures of Comparative Example 3 and Example 1 of this application, wherein... Figure 3 (a) in the figure shows the grain structure of Comparative Example 3. Figure 3 (b) in the figure represents the grain structure of Example 1.

[0027] Figure 4 This is a schematic diagram comparing the grain structures of Comparative Example 4 and Example 1 of this application, wherein... Figure 4 (a) in the figure shows the grain structure of Comparative Example 4. Figure 4 (b) in the figure represents the grain structure of Example 1. Detailed Implementation

[0028] The principles and features of this application are described below with reference to embodiments. The examples are for illustrative purposes only and are not intended to limit the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0029] As a core starting component of refrigeration equipment compressors, the performance of PTC (Positive Temperature Coefficient) thermistors directly determines the energy consumption level and operational reliability of the equipment. Currently, PTC thermistors used for starting refrigerator and freezer compressors generally suffer from high power consumption and insufficient reliability, making them unsuitable for meeting the energy-saving and environmental protection requirements of next-generation refrigeration equipment. Taking mainstream industry specifications as an example: for a PTC starter chip with a chip size of φ (diameter) 15.8mm × t (thickness) 2.5mm, a Curie temperature (Tc25) of 135±7℃ at 25℃, and a resistance value (R25) of 15Ω±20% at 25℃, the steady-state power consumption of existing products, both domestically and internationally, is generally between 2.6W and 2.8W. Furthermore, the destructive voltage under high-voltage conditions is only about 700V. This not only leads to high energy consumption in refrigeration equipment operation but also makes the component prone to failure due to voltage fluctuations, increasing equipment maintenance costs. There are three pairs of technical contradictions that are difficult to balance in relation to the core factors affecting the power consumption and reliability of PTC thermistors, as follows: (1) The contradiction between chip size and reliability: According to Joule's law, under the same current conditions, the smaller the chip size, the more concentrated the heat generation per unit volume and the lower the power consumption (theoretically, a 10% reduction in chip size can reduce power consumption by 8%~10%). However, the reduction in size will lead to a decrease in the strength of the chip structure, and microcracks are easily generated due to stress concentration during the hot and cold cycle, which significantly reduces the product's impact resistance and service life. (2) The contradiction between Curie temperature and recovery time: Curie temperature (Tc) is the critical temperature at which the resistance of PTC element changes abruptly. Lowering the Curie temperature can allow the element to enter a high-resistance state at a lower temperature, reducing ineffective heat generation and thus reducing power consumption (power consumption can be reduced by 5%~7% for every 10°C decrease in Tc); however, under the existing ceramic material formulation, a decrease in Curie temperature will lead to a decrease in the charge migration rate within the ceramic grains, which will prolong the time for the element to recover from a high-resistance state to a low-resistance state (when Tc drops from 135°C to 120°C, the recovery time increases from 5s to more than 8s), thereby affecting the frequent start-up response speed of the compressor. (3) The contradiction between chip temperature rise and thermal shock resistance: The higher the chip temperature rise, the lower the heat dissipation efficiency of the component and the lower the surface power consumption (for every 10°C increase in temperature, the measured power consumption can be reduced by 3%~5%). However, excessive temperature rise will exacerbate the difference in thermal expansion coefficient between the chip and the electrode interface, leading to interface peeling or cracking of the ceramic substrate, which will reduce the product's thermal shock resistance (usually measured by the number of thermal cycles from -40°C to 125°C) from more than 1,000 times to less than 500 times, seriously affecting reliability. The root of the contradictions in traditional technologies lies in the defects in the formulation design and preparation process of existing PTC ceramics: On the one hand, existing ceramic materials mostly adopt a single BaTiO3-based formulation, with only a small amount of Sr and Ca elements added for doping modification. The ratio of semiconductor agents (such as Nb2O5) and sintering aids lacks systematic optimization, resulting in uneven growth of ceramic grains and insufficient density, making it difficult to balance Curie temperature control and charge transfer efficiency. On the other hand, the preparation process suffers from uneven mixing in wet ball milling (coarse control of the ratio of raw materials, balls, and water, and ball milling time and frequency not matching the characteristics of raw materials), unreasonable pre-calcination temperature and holding time (often using high-temperature and long-term calcination above 1200℃, which easily leads to the loss of volatile components such as PbO), and a lack of precise temperature control in the molding and sintering processes, which further amplify the defects in the formulation and fail to maximize the performance of the ceramic material.

[0030] Based on this, this application provides a low-power variable frequency starter PTC thermistor and its preparation method. In the formulation, by optimizing the BaCO3-TiO2-SrCO3-CaCO3-PbO five-element main formulation system, high-efficiency glass phase materials (such as TiO2-SiO2-Al2O3 composite system) and manganese additive [Mn(NO3)2] are introduced to regulate grain growth. Combined with precise ball milling / sand milling mixed abrasive process, pre-calcination and segmented calcination, and pressing molding processes, a synergistic improvement in low power consumption and high reliability is achieved.

[0031] Specifically, in the first aspect, this application provides a low-power PTC thermistor for frequency conversion starting, comprising a PTC ceramic matrix, a glass phase material, a semiconductor agent, and a manganese additive; wherein, by mass percentage, it comprises the following raw materials: BaCO3: 48%~62%, TiO2: 22%~38%, SrCO3: 0.5%~1.2%, CaCO3: 4%~8%, PbO: 4%~8%, glass phase material: 0.3%~0.6%, semiconductor agent: 0.25%~0.45%, Mn(NO3)2: 0.3%~0.6%. The PTC chip produced using the formulation of this application has advantages such as low voltage effect, high ceramic withstand voltage level, high temperature coefficient, high reliability, and low power consumption. SrCO3 and PbO work synergistically. SrCO3 can suppress excessive grain growth and refine the grains to reduce local electric field concentration; PbO optimizes the Curie temperature by regulating lattice distortion. The combination of the two improves microstructure uniformity and lays the foundation for low power consumption based on temperature characteristics. CaCO3 plays a structural strengthening role, while Ca... 2+ Integrating into the crystal lattice can increase the density of ceramics and reduce internal voids, thereby improving voltage withstand levels (avoiding electric field concentration caused by voids) and reducing leakage current, indirectly reducing power consumption. Glass phase materials (such as SiO2) can improve the grain boundary layer structure, enhance grain boundary insulation performance, further suppress voltage effects, and simultaneously enhance the structural stability of the ceramic. Mn 2+ It can capture oxygen vacancies in the crystal lattice, reduce defect conductivity, improve the sensitivity of the temperature coefficient to temperature changes, and enhance the ceramic's resistance to thermal shock. Through the precise proportioning and synergistic effect of multiple components, the PTC ceramic matrix prepared by the formulation system of this application achieves a comprehensive performance breakthrough with small voltage effect, high withstand voltage, high temperature coefficient, high reliability, and low power consumption. It completely solves the technical problems of imbalance between voltage effect and PTC effect and insufficient safety and reliability in traditional formulations, and provides key formulation support for the development of low-power frequency conversion starting PTC thermistors.

[0032] In a specific embodiment, the glass phase material includes at least one of TiO2, SiO2, Al2O3, Li2CO3, and BN.

[0033] In a specific embodiment, the semiconductor agent includes at least one of Nb2O5, Sm2O3, and Er2O3. Preferably, the semiconductor agent uses equal masses of Sm2O3 and Er2O3, abandoning the traditional donor doping mode of single or simple mixture of Nb2O5, Y2O3, and La2O3. The Sm2O3 released from the two rare earth oxides... 3+ With Er 3+Sm can achieve ceramic semiconductorization through non-equivalent substitution and suppress aberrant transitions of charge carriers under high voltage by means of a stepped energy level distribution. Compared with the single energy level of traditional doped systems, Sm 3+ With Er 3+ The energy level difference can build multi-level potential barriers, which can significantly reduce the voltage effect and avoid performance fluctuations caused by single doping, thus providing core support for the stable presentation and safety improvement of the PTC effect.

[0034] In a specific implementation, the formula for the PTC ceramic matrix is ​​(Ba 1-x-y-z Sr x Pb y Ca z TiO3, where x ranges from 1% to 5%, y ranges from 5% to 8%, z ranges from 12% to 22%, and the total amount of x + y + z does not exceed 35%.

[0035] Secondly, based on a general inventive concept, this application also discloses a method for preparing a low-power frequency converter starting PTC thermistor, comprising the following steps: S1. The semiconductor agent is mixed with nano-alumina powder and then coated and modified to obtain a coated semiconductor agent.

[0036] In a specific embodiment, the coated semiconductor agent is prepared by the following method: the semiconductor agent is mixed with 0.05wt%~0.08wt% of nano-alumina powder, and then processed by an air jet mill at a speed of 25000rpm~30000rpm for 12min~18min. The nano-alumina can form a dense protective layer on the surface of the semiconductor agent, preventing excessive volatilization during pre-calcination, ensuring uniform semiconductor effect, supporting both size reduction (reducing stress concentration caused by uneven composition inside the chip) and maintaining product reliability (reducing the risk of failure caused by composition fluctuations).

[0037] S2. Weigh the remaining raw materials and mix them with the coating semiconductor agent by wet ball milling and then dry them to obtain ceramic material.

[0038] In a specific embodiment, the mass ratio of raw materials, balls and water in wet ball milling is 1:(1~1.5):(1~1.5), the ball milling frequency is 30Hz~50Hz, and the ball milling time is 30h~35h.

[0039] S3. The ceramic material is pre-calcined at 1160℃~1200℃ for 3.5h~4.5h, and then crushed to obtain the pre-calcined material.

[0040] S4. Manganese nitrate, glass powder and rare earth oxides are dispersed in ethanol to prepare a coating solution, and the pre-calcined material is coated with the coating solution. After drying and heat treatment, the modified pre-calcined material is obtained.

[0041] In a specific embodiment, the concentration of manganese nitrate in the coating solution is 0.1wt%~0.3wt%, the concentration of glass powder is 0.05wt%~0.15wt%, and the concentration of rare earth oxides is 0.02wt%~0.08wt%. Since traditional manganese additives are added all at once during the ball milling stage, manganese elements simultaneously enter the crystal lattice and grain boundaries. This application, however, precisely enriches most of the manganese elements and the newly added AST glass powder and rare earth oxides at the grain boundaries through early-stage grain boundary coating. The Mn enriched at the grain boundaries can more effectively form acceptor states, greatly enhancing the grain boundary barrier and thus strengthening the PTC effect. Even if the Curie temperature of the basic formulation (BaTiO3 solid solution) is lowered, the enhanced PTC effect ensures that the resistance rapidly increases at high temperatures, thereby shortening the recovery time. The glass powder optimizes the distribution of the grain boundary phase, forming a thinner and more uniform insulating layer, reducing grain boundary capacitance, and helping to improve the response speed and stability at high frequencies. Rare earth oxides can suppress abnormal grain growth and refine grains, laying the foundation for subsequent size reduction without compromising reliability.

[0042] In a specific embodiment, the glass powder is preferably AST glass powder (i.e., Al2O3-SiO2-TiO2), and the rare earth oxide is preferably yttrium oxide.

[0043] In a specific embodiment, the drying heat treatment includes: drying the coated powder at 80℃~120℃, and then heat-treating it at 600℃~800℃ for 1h~2h.

[0044] S5. Mix the modified precalcined material with dispersant and defoamer to form a slurry.

[0045] In a specific embodiment, the mixed abrasive is the secondary abrasive process of this application, which adopts sand milling combined with the ball milling process of the previous primary abrasive. This enables the prepared ceramic material to have excellent characteristics such as high spherical ratio, uniform particle size, and no hollows. On the one hand, it significantly improves the loose density of the ceramic material, ensuring uniform filling of raw materials during subsequent molding and reducing density differences inside the green body; on the other hand, it significantly reduces the average particle size D of the ceramic material. 50 This technology effectively solves the problem of easy agglomeration of ultrafine powders, avoiding structural defects in ceramic materials caused by agglomerates. The PTC ceramic matrix prepared by this mixed abrasive technology has the advantages of uniform microstructure and stable performance.

[0046] In a specific embodiment, the mass of the dispersant is 0.08% to 0.12% of the pre-calcined material. The mass of the defoamer is 0.002% to 0.003% of the pre-calcined material.

[0047] In a specific implementation, the rotation speed of the mixed abrasive is 1100 rpm to 1300 rpm, and the time is 20 min to 40 min.

[0048] S6. The slurry is mixed with the binder and plasticizer and then subjected to spray granulation, pressing and calcination in sequence to obtain ceramic sheets.

[0049] In a specific embodiment, the mass of the adhesive is 15% to 18% of the slurry; the mass of the plasticizer is 0.6% to 1.2% of the slurry.

[0050] In a specific embodiment, the green blank obtained after compression molding preferably has dimensions of Φ (18mm~20mm, diameter) × t (2mm~3mm, thickness) 3.0mm, and a green blank mass of 2.5g~3g. This application appropriately reduces the chip size and lowers the chip's Curie temperature. On the one hand, while ensuring reliability is not compromised, the chip volume is reasonably reduced, reducing the overall heat generation per unit time and directly reducing energy loss. On the other hand, by adjusting the formula, the chip's Curie temperature is optimized to a reasonable range suitable for frequency conversion start-up scenarios, allowing the chip to enter a high-resistance state at a lower temperature, avoiding ineffective heat generation.

[0051] In a specific embodiment, the calcination treatment includes the following steps: heating to 600℃~700℃ at a rate of 2℃ / min~3℃ / min and holding for 60min~90min to fully remove binders and plasticizers; introducing a nitrogen-oxygen mixed atmosphere with an oxygen content of 1%~5% and heating to 1150℃~1250℃ at a rate of 4℃ / min~5℃ / min and holding for 30min~60min to promote grain growth and initial densification; switching to pure oxygen or air with an oxygen content of 10%~21% and heating to a peak temperature of 1320℃~1350℃ at a rate of 3℃ / min~4℃ / min and holding for 30min~50min to optimize the oxygen vacancy concentration at grain boundaries and enhance the grain boundary barrier; cooling to 900℃ at a rate of 3℃ / min~5℃ / min and cooling to room temperature in the furnace. Through the segmented temperature control and atmosphere regulation of this application, the decoupling of internal grain densification and grain boundary layer optimization can be achieved. The low oxygen partial pressure during the intermediate temperature stage facilitates grain growth and the removal of pores, resulting in a high-density ceramic body, which is fundamental to ensuring mechanical strength and reliability. As size decreases, the tolerance for internal defects decreases, making high density crucial. Simultaneously, the oxygen-rich environment during the high-temperature stage effectively heals oxygen vacancies at grain boundaries, resulting in a higher and more stable grain boundary barrier. A stable and uniform grain boundary structure is less prone to microcracks or performance degradation when subjected to severe thermal shock (i.e., chip temperature rise). Finally, controlled-rate cooling effectively releases the thermal stress generated during sintering, further improving thermal shock resistance.

[0052] S7. Nickel and silver layers are prepared on the surface of a ceramic sheet by sputtering and printing, respectively, to obtain a low-power frequency conversion starting PTC thermistor.

[0053] In a specific embodiment, the thickness of the nickel layer is 0.4μm to 0.6μm, and the thickness of the silver layer is 3μm to 8μm.

[0054] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0055] The raw materials and instruments used in the following examples and comparative examples include, but are not limited to: Barium carbonate (BaCO3), purity 99.5%, manufactured by Sichuan Mianyang Yuanda New Materials Co., Ltd.

[0056] Strontium carbonate (SrCO3), purity 99.5%, manufactured by Chongqing Dazu Hongdie Strontium Industry Co., Ltd.

[0057] Calcium carbonate (CaCO3), purity 99.3%, manufactured by Shandong Dongying New Century Optoelectronic Materials Co., Ltd.

[0058] Lead oxide (PbO), purity 99.5%, manufactured by Guangdong Whale Shark Chemical Co., Ltd.

[0059] Titanium dioxide (TiO2), with a purity of 99.9%, is manufactured by Hubei Tianci Electronic Materials Co., Ltd.

[0060] Lanthanum oxide (La2O3), 3N standard, manufactured by Jiangxi Zhongli Tantalum & Niobium Co., Ltd.

[0061] Samarium oxide (Sm2O3), 3N standard, manufactured by Jiangxi Zhongli Tantalum-Niobium Co., Ltd.

[0062] Erbium trioxide (Er2O3), AR standard, manufactured by Shandong Desheng Chemical Co., Ltd.

[0063] Niobium pentoxide (Nb2O5), 4N standard, manufactured by Jiangxi Zhongli Tantalum-Niobium Co., Ltd.

[0064] Silicon dioxide (SiO2), AR standard, manufactured by Xilong Scientific Co., Ltd.

[0065] Aluminum oxide (Al2O3), AR standard, manufactured by Sinopharm Chemical Reagent Co., Ltd.

[0066] Lithium carbonate (Li2CO3), AR standard, manufactured by Sinopharm Chemical Reagent Co., Ltd.

[0067] Boron nitride (BN), with a purity of 99.9%, is manufactured by Hebei Keze Metal Materials Co., Ltd.

[0068] Manganese nitrate [Mn(NO3)2], AR standard, manufactured by Chongqing Chuandong Chemical Co., Ltd.

[0069] Electronic balance AL-104 (Mettler-Toledo Shanghai Co., Ltd.), wet rubber-lined ball mill FT-200 (Panjin Xianglong Grinding Technology Co., Ltd.), rod pin horizontal sand mill TBJ-60L (Quite (Shanghai) Electromechanical Technology Co., Ltd.), fully automatic tunnel pusher plate pulverizing furnace TL-1I / II20M (Chengdu Langchen Electronics Co., Ltd.), continuous sputtering coating production line LP-1000B (Hangzhou Bifanco Electronic Technology Co., Ltd.), GL type centrifugal spray granulation dryer G-50L (Wuxi Atez Intelligent Equipment Co., Ltd.), fully automatic rotary tablet press MC-RP550 (Dongguan) Kimura Machinery Co., Ltd.), DON168-10 Silver Printing and Drying Integrated Machine (Dongguan Sanfu Electromechanical Co., Ltd.), WD-2-6 Atmosphere Mesh Belt Silver Burning Furnace (Chengdu Langchen Electronics Co., Ltd.), TDB-216SCBF Electric Heating Blower Drying Oven (Chengdu Xingtianyu Experimental Instrument Co., Ltd.), DMM6500 Resistance Meter (KEITHEY), R / T Resistance Temperature Characteristic Tester (Huazhong University of Science and Technology), V / I Withstand Voltage Tester (Huazhong University of Science and Technology), JL-1155 Laser Particle Size Analyzer (Chengdu Jingxin Powder Testing Equipment Co., Ltd.), HJ1 Optical Microscope (Nanjing Nanpai Technology Co., Ltd.).

[0070] Example 1 This embodiment provides a low-power variable frequency starter PTC thermistor, which comprises the following raw materials by mass percentage: BaCO3: 60%, TiO2: 26%, SrCO3: 1.2%, CaCO3: 6.3%, PbO: 5%, glass phase material SiO2: 0.5%, semiconductor agent (equal mass of Sm2O3 + Er2O3): 0.4%, Mn(NO3)2: 0.6%.

[0071] The low-power variable frequency starter PTC thermistor of this embodiment is prepared by the following method: (1) Determine the high-purity raw materials to be used based on the target product and weigh them accurately.

[0072] (2) The semiconductor agent is mixed with nano alumina powder at a mass of 0.05wt%, and then coated and modified by air jet mill at a speed of 25000rpm for 15min to obtain the coated semiconductor agent.

[0073] (3) The raw materials other than the semiconductor agent and the coated semiconductor agent are mixed by wet ball milling and then dried in a drying oven at 180°C to obtain ceramic material. The total amount of raw materials and the mass ratio of agate balls to water in the wet ball milling are 1:1.5:1.5, the ball milling frequency is 45Hz, and the ball milling time is 32h.

[0074] (4) Take the ceramic material out of the drying oven, put it into the corundum mullite sagger, pre-calcine it at 1180℃ for 4 hours, and then crush it to obtain the pre-calcined material.

[0075] (5) Manganese nitrate, AST glass powder, and rare earth oxides were dispersed in ethanol to prepare a coating solution. The pre-calcined material was coated with the coating solution, and the coated powder was dried at 80°C. Then, it was heat-treated at 600°C for 2 hours to obtain the modified pre-calcined material. The concentration of manganese nitrate in the coating solution was 0.1 wt%, the concentration of AST glass powder was 0.05 wt%, and the concentration of rare earth oxides was 0.02 wt%.

[0076] (6) The modified precalcined material, AKM dispersant (0.08 wt% of the modified precalcined material), and F102 defoamer (0.002 wt% of the modified precalcined material) are put into a sand mill for mixing and grinding to obtain a slurry.

[0077] The abrasive mixing process was conducted twice, each time for 20 minutes. The abrasive mixing speed was 1100 rpm, and the weight ratio of abrasive to balls to water was 1:0.4:2.

[0078] (7) Pour the slurry into the slurry tank, add 13wt% PVA adhesive (17wt% of the slurry) and LU-6418 plasticizer (1.0wt% of the slurry), mix and then pour into the spray granulator for spray granulation.

[0079] (8) The granulated powder is formed in a rotary tablet press with a pressure of 35T. The size of the formed green body is Φ (18.68mm, diameter) × t (3.0mm, thickness), and the mass of the green body is 2.95g.

[0080] (9) The formed green body is placed in a tunnel sintering furnace for sintering treatment, including: heating to 600°C at a rate of 2°C / min and holding for 60 min; introducing a nitrogen-oxygen mixed atmosphere with an oxygen content of 5% and heating to 1150°C at a rate of 5°C / min and holding for 30 min; switching to pure oxygen and heating to a peak temperature of 1350°C at a rate of 3°C / min and holding for 50 min; cooling to 900°C at a rate of 5°C / min and cooling to room temperature with the furnace to obtain ceramic tiles.

[0081] (10) Sputter a 0.4 μm thick layer of metallic nickel on the surface of the sintered ceramic sheet, and then screen print a 5 μm thick layer of silver paste on the surface of the metallic nickel layer. Burn and infiltrate at 560℃ for 20 min to form a layer of metallic silver, and obtain a low power consumption frequency conversion starter PTC thermistor.

[0082] Example 2 This embodiment provides a low-power variable frequency starter PTC thermistor, which comprises the following raw materials by mass percentage: BaCO3: 62%, TiO2: 22%, SrCO3: 0.5%, CaCO3: 5.9%, PbO: 8%, glass phase material SiO2: 0.6%, semiconductor agent (equal mass of Sm2O3 + Er2O3): 0.4%, Mn(NO3)2: 0.6%.

[0083] The low-power variable frequency starter PTC thermistor of this embodiment is prepared by the following method: (1) Determine the high-purity raw materials to be used based on the target product and weigh them accurately.

[0084] (2) The semiconductor agent is mixed with nano-alumina powder accounting for 0.08 wt% of its mass, and then coated and modified by air jet mill at a speed of 30,000 rpm for 18 min to obtain the coated semiconductor agent.

[0085] (3) The raw materials other than the semiconductor agent and the coated semiconductor agent are mixed by wet ball milling and then dried in a drying oven at 180°C to obtain ceramic material. The total amount of raw materials and the mass ratio of agate balls to water in the wet ball milling are 1:1.5:1, the ball milling frequency is 50Hz, and the ball milling time is 35h.

[0086] (4) Take the ceramic material out of the drying oven, put it into the corundum mullite sagger, pre-calcine it at 1200℃ for 4.5h, and then crush it to obtain the pre-calcined material.

[0087] (5) Manganese nitrate, AST glass powder, and rare earth oxides were dispersed in ethanol to prepare a coating solution. The pre-calcined material was coated with the coating solution, and the coated powder was dried at 120°C and then heat-treated at 800°C for 1 hour to obtain the modified pre-calcined material. The concentration of manganese nitrate in the coating solution was 0.3 wt%, the concentration of AST glass powder was 0.15 wt%, and the concentration of rare earth oxides was 0.08 wt%.

[0088] (6) The modified precalcined material, AKM dispersant (0.12 wt% of the modified precalcined material), and F102 defoamer (0.003 wt% of the modified precalcined material) are put into a sand mill for mixing and grinding to obtain a slurry.

[0089] The abrasive mixing process was conducted twice, each time for 10 minutes. The abrasive mixing speed was 1300 rpm, and the weight ratio of abrasive to balls to water was 1:0.5:3.0.

[0090] (7) Pour the slurry into the slurry tank, add 13wt% PVA adhesive (18wt% of the slurry) and LU-6418 plasticizer (1.2wt% of the slurry), mix and then pour into the spray granulator for spray granulation.

[0091] (8) The granulated powder is formed in a rotary tablet press with a pressure of 35T. The size of the formed green body is Φ (18.68mm, diameter) × t (3mm, thickness), and the mass of the green body is 2.97g.

[0092] (9) The formed green body is placed in a tunnel sintering furnace for sintering treatment, including: Heat to 700℃ at a rate of 3℃ / min and hold for 90min; A nitrogen-oxygen mixed atmosphere with an oxygen content of 5% was introduced, and the temperature was increased to 1250℃ at a rate of 5℃ / min and held for 30min. Switch to air with an oxygen content of 21%, heat it to a peak temperature of 1350℃ at a rate of 4℃ / min, and hold it at that temperature for 30 minutes. The ceramic slab was cooled to 900°C at a rate of 3°C / min and then cooled to room temperature in the furnace to obtain the ceramic slab.

[0093] (10) A layer of 0.6 μm thick metallic nickel is sputtered on the surface of the sintered ceramic sheet, and then a layer of 8 μm thick silver paste is screen printed on the surface of the metallic nickel layer. The paste is then fired at 560°C for 20 min to form a layer of metallic silver, thus obtaining a low-power frequency conversion starter PTC thermistor.

[0094] Example 3 This embodiment provides a low-power variable frequency starter PTC thermistor, which comprises the following raw materials by weight percentage: BaCO3: 53%, TiO2: 31%, SrCO3: 0.8%, CaCO3: 7.9%, PbO: 6%, glass phase material SiO2: 0.3%, semiconductor agent (Sm2O3+Er2O3): 0.4%, Mn(NO3)2: 0.6%.

[0095] The low-power variable frequency starter PTC thermistor of this embodiment is prepared by the following method: (1) Determine the high-purity raw materials to be used based on the target product and weigh them accurately.

[0096] (2) The semiconductor agent is mixed with nano-alumina powder accounting for 0.06 wt% of its mass, and then coated and modified by air jet mill at a speed of 25000 rpm for 15 min to obtain the coated semiconductor agent.

[0097] (3) The raw materials other than the semiconductor agent and the coated semiconductor agent are mixed by wet ball milling and then dried in a drying oven at 180°C to obtain ceramic material. The total amount of raw materials, the mass ratio of agate balls to water in wet ball milling is 1:1:1.5, the ball milling frequency is 30Hz, and the ball milling time is 35h.

[0098] (4) Take the ceramic material out of the drying oven, put it into the corundum mullite sagger, pre-calcine it at 1160℃ for 4 hours, and then crush it to obtain the pre-calcined material.

[0099] (5) Manganese nitrate, AST glass powder and rare earth oxides are dispersed in ethanol to prepare a coating solution, and the pre-calcined material is coated with the coating solution. The coated powder is dried at 100°C and then heat-treated at 750°C for 1 hour to obtain the modified pre-calcined material.

[0100] The coating solution contained 0.1 wt% manganese nitrate, 0.1 wt% AST glass powder, and 0.04 wt% rare earth oxides.

[0101] (6) The modified precalcined material, AKM dispersant (0.1 wt% of the modified precalcined material), and F102 defoamer (0.002 wt% of the modified precalcined material) are put into a sand mill for mixing and grinding to obtain a slurry.

[0102] The abrasive mixing process was conducted twice, each time for 15 minutes. The abrasive mixing speed was 1200 rpm, and the weight ratio of abrasive to balls to water was 1:0.5:2.0.

[0103] (7) Pour the slurry into the slurry tank, add 13wt% PVA adhesive (15wt% of the slurry) and LU-6418 plasticizer (1wt% of the slurry), mix and then pour into the spray granulator for spray granulation.

[0104] (8) The granulated powder is formed in a rotary tablet press with a pressure of 35T. The size of the formed green body is Φ (18mm, diameter) × t (3mm, thickness), and the mass of the green body is 2.9g.

[0105] (9) The formed green body is placed in a tunnel sintering furnace for sintering treatment, including: Heat to 700℃ at a rate of 3℃ / min and hold for 90min; A nitrogen-oxygen mixed atmosphere with an oxygen content of 3% was introduced, and the temperature was raised to 1150℃ at a rate of 5℃ / min and held for 30min. Switch to air with an oxygen content of 17%, heat it to a peak temperature of 1325℃ at a rate of 4℃ / min, and hold it at that temperature for 30 minutes. The ceramic slab was cooled to 900°C at a rate of 3°C / min and then cooled to room temperature in the furnace to obtain the ceramic slab.

[0106] (10) Sputter a 0.5 μm thick layer of metallic nickel on the surface of the sintered ceramic sheet, and then screen print a 5 μm thick layer of silver paste on the surface of the metallic nickel layer. Burn and infiltrate at 560℃ for 20 min to form a layer of metallic silver, and obtain a low power consumption frequency conversion starter PTC thermistor.

[0107] Comparative Example 1 The difference between this comparative example and Example 1 is that SrCO3 is not doped, and the PbO content is adjusted to 6.2%. The resulting ceramic sheet has the following grain structure. Figure 1 As shown (metallurgical microscope, 400x magnification), among which Figure 1 (a) in the text represents the product of Comparative Example 1. Figure 1 (b) is the product of Example 1. (From...) Figure 1 It can be seen that the product of Comparative Example 1 has relatively coarse grains, with more irregular grains such as square and triangular grains, fewer grain boundaries, stronger voltage effect, and weaker voltage resistance of the ceramic sheet. The product of Example 1 has a uniform grain structure, smaller grain size, more grain boundaries, smaller voltage effect, and stronger voltage resistance of the ceramic sheet. This indicates that the addition of SrCO3 to the material has a significant effect on inhibiting grain growth in the sintered ceramic blank, and grain refinement can reduce voltage effect and improve voltage resistance.

[0108] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not dope CaCO3, but instead uses BaCO3. The resulting ceramic sheet has the following grain structure. Figure 2 As shown (metallurgical microscope, 400x magnification), among which Figure 2 (a) in the text represents the product of Comparative Example 2. Figure 2 (b) is the product of Example 1. (From...) Figure 2 It can be seen that the microstructure of the product in Comparative Example 2 has huge grains (up to 40 μm), and many irregular grains such as prismatic grains. In contrast, the product in Example 1 has significantly smaller grain size (down to 5 μm) and more grain boundaries, indicating that the addition of CaCO3 has a significant effect on refining grains and inhibiting grain growth.

[0109] Comparative Example 3 The difference between this comparative example and Example 1 is that the undoped Sm2O3 and Er2O3 are replaced with yttrium oxide (Y2O3). The resulting ceramic sheet has the following grain structure. Figure 3 As shown (metallurgical microscope, 400x magnification), among which Figure 3 (a) in the text represents the product of Comparative Example 3. Figure 3 (b) is the product of Example 1. (From...) Figure 3It can be seen that the product of Comparative Example 3 has relatively large grains, with more irregular grains such as square and triangular crystals, fewer grain boundaries, stronger voltage effect, and weaker voltage resistance of the ceramic sheet; while the product of Example 1 has a uniform grain structure, smaller grain size, more grain boundaries, smaller voltage effect, and stronger voltage resistance of the ceramic sheet. This shows that the novel donor doping of this application has a significant effect on refining grains, improving the density of the ceramic body, and reducing voltage effect.

[0110] Comparative Example 4 The difference between this comparative example and Example 1 is that the traditional ball milling technique is used in the mixed abrasive process in step (6), instead of sand milling. The resulting ceramic wafer has the following grain structure: Figure 4 As shown (metallurgical microscope, 400x magnification), among which Figure 4 (a) in the text represents the product of Comparative Example 4. Figure 4 (b) is the product of Example 1. (From...) Figure 4 It can be seen that the mixed abrasive process of ball milling and sand milling produces ceramic materials with a high proportion of spherical particles, uniform particle size, no hollows, and significantly improved loose packing density and average particle size D. 50 The density of the powder decreased significantly. In contrast, powder granulated using only traditional ball milling processes has more defects; for example, the loose packing density of powder granulated using traditional ball milling is 1.1 g / cm³. 3 The bulk density of the powder prepared by the mixed abrasive process in this application is approximately 1.6 g / cm³. 3 The powder density is significantly improved. For example, the average particle size D of the powder after secondary grinding in traditional ball milling process is reduced. 50 The average particle size D of the powder after secondary abrasive grinding in this application is around 1.5 μm. 50 At around 0.7μm, the average particle size D is lower than that of traditional ball milling processes. 50 The smaller average particle size of this application results in a larger specific surface area for the powder, allowing for repeated powder contact during sintering, leading to higher powder activity, a lower sintering temperature, and suppression of lead volatilization. Simultaneously, the lower sintering temperature also avoids the formation of large, anomalous grains, further ensuring grain uniformity.

[0111] Experimental Example The low-power frequency conversion starting PTC thermistor of Embodiment 1 of this application was processed into a size of Φ15.8mm×t2.5mm and its performance was tested with the conventional product EPCOS. The results are shown in Table 1.

[0112] Table 1 Performance Comparison Data

[0113] As shown in Table 1, the low-power PTC thermistor for frequency conversion starting in this application, while having comparable product size, Curie temperature, and resistance value to commercially available EPCOS resistors, consumes approximately 0.5W to 0.6W less power than EPCOS products, achieving low power consumption characteristics. Simultaneously, the product's static voltage, dynamic withstand voltage, and high-voltage cycle test levels are significantly improved, resulting in a substantial increase in product reliability. For PTC chips with specifications of Φ15.8mm×t2.5mm, a Curie temperature (Tc25) of 135±7℃ at 25℃, and a resistance value (R25) of 15Ω±20% at 25℃, this application reduces the size of the PTC chip through synergistic regulation of the formula and process (such as grain refinement to reduce heat generation per unit volume and grain boundary barrier optimization to reduce leakage current). This reduces the steady-state power consumption from the existing technology's 2.6W~2.8W to approximately 2.1W, a power consumption reduction of 20%, directly reducing the operating energy consumption of refrigeration equipment such as refrigerators, air conditioners, and freezers.

[0114] In summary, this application has at least the following advantages: (1) This application adopts a Sr-Pb co-doped formulation system. Through the synergistic distribution of Sr-Pb in the grain boundary region, a double grain boundary barrier layer is constructed, which refines the ceramic grain size and achieves uniform and refined control of the grains. Furthermore, the refined grains increase the number of grain boundaries, making the grain boundary barrier multi-level distributed, thus improving the overall voltage breakdown resistance. On the other hand, Sr 2+ With Pb 2+ Uniform solid solution within the crystal lattice reduces lattice defects, lowers carrier scattering losses within the lattice, and avoids abnormal resistance fluctuations caused by defect conductivity under high voltage. Simultaneously, by adjusting Sr... 2+ With Pb 2+ The optimal mass ratio allows for on-demand control of the Curie temperature while leveraging the inhibitory effect of Sr-Pb co-doping on grain growth, ensuring increased density of the ceramic matrix. This avoids the imbalance between Curie temperature control and microstructure stability caused by traditional single doping, laying the microstructure foundation for the fabrication of small-sized, high-reliability PTC devices.

[0115] (2) In this application, CaCO3 is added to the formula as a refining agent. CaCO3 will decompose into Ca during the sintering process. 2+ With CO3 2- , where Ca 2+ It can interact with the Ba in the BaTiO3 perovskite structure (ABO3). 2+ Lattice substitution occurs due to Ca. 2+ The ionic valence state of Ba 2+ Consistent, its solid solution behavior will change the donor impurities (such as Nb) in the crystal lattice. 2+ 、Sm 3+The distribution of donor ions (such as semiconductor ions) can be controlled to regulate the donor concentration within the grains. This allows for uniform dispersion of donor ions, reducing both the bulk resistivity of the grains and the abnormal rise of the grain boundary barrier by suppressing excessive enrichment of donor ions in the grain boundary region, thus synergistically reducing grain boundary resistance and optimizing the overall resistivity of the ceramic. The voltage withstand level of PTC ceramics essentially depends on the density of its microstructure and the insulating properties of its grain boundaries. The addition of CaCO3 can improve voltage withstand performance in two ways: firstly, densification reduces voids and microcracks within the ceramic, preventing electrical breakdown caused by localized electric field concentration under high voltage due to these defects; the reduced porosity allows for a more uniform electric field distribution within the ceramic, preventing localized field strength from exceeding the dielectric breakdown threshold; secondly, CaCO3... 2+ Moderate segregation in the grain boundary region can optimize the insulation properties of the grain boundary layer, Ca 2+ The presence of [something] can inhibit the migration of oxygen vacancies in the grain boundary region, reduce the conductive paths formed by the accumulation of oxygen vacancies, and thus improve the insulation strength of the grain boundary.

[0116] (3) This application uses a co-doped system of Sm2O3 and Er2O3 as the donor doping source, Sm 3+ With Er 3+ The difference in ionic radius can break the aggregation trend of single ions, and achieve a uniform distribution of donor ions in the lattice through the size complementarity effect. This avoids the formation of local high-concentration carrier regions due to ion aggregation, and further suppresses the voltage effect caused by increased leakage current. 3+ With Er 3+ The ionic radius is smaller than that of Y. 3+ Rare earth elements are more likely to segregate towards grain boundary regions, forming a uniformly thick rare earth-enriched grain boundary layer. This grain boundary layer enhances the blocking effect on charge carriers, raises the grain boundary barrier, and thus significantly enhances the temperature sensitivity characteristics of ceramics, ensuring rapid response of components under temperature fluctuation conditions. Meanwhile, Sm... 3+ With Er 3+ Co-doping can reduce the generation of oxygen vacancies, and the reduction of oxygen vacancies can avoid grain boundary barrier fluctuations caused by oxygen vacancies acting as carrier traps, thereby further improving the stability of the temperature coefficient.

[0117] While specific embodiments of this application have been described in detail, this should not be construed as limiting the scope of protection of this application. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this application.

Claims

1. A low-power PTC thermistor for variable frequency starting, characterized in that, It includes PTC ceramic matrix, glass phase material, semiconductor agent, and manganese additive; among which, By mass percentage, it includes the following raw materials: BaCO3: 48%~62%, TiO2: 22%~38%, SrCO3: 0.5%~1.2%, CaCO3: 4%~8%, PbO: 4%~8%, glass phase material: 0.3%~0.6%, semiconductor agent: 0.25%~0.45%, Mn(NO3)2: 0.3%~0.6%; among which, The glass phase material includes at least one selected from TiO2, SiO2, Al2O3, Li2CO3, and BN; the semiconductor agent includes at least one selected from Nb2O5, Sm2O3, and Er2O3; wherein... The low-power variable frequency starter PTC thermistor has a power consumption of <2.2W, a static withstand voltage of >900V, and a dynamic withstand voltage of >500V.

2. The low-power variable frequency starter PTC thermistor according to claim 1, characterized in that, The glass phase material is SiO2.

3. The low-power variable frequency starter PTC thermistor according to claim 1, characterized in that, The semiconductor agent comprises equal masses of Sm2O3 and Er2O3.

4. The low-power variable frequency starter PTC thermistor according to claim 1, characterized in that, The formula for the PTC ceramic matrix is ​​(Ba 1-x-y-z Sr x Pb y Ca z TiO3, where x ranges from 1% to 5%, y ranges from 5% to 8%, z ranges from 12% to 22%, and the total amount of x + y + z does not exceed 35%.

5. A method for preparing a low-power variable frequency starter PTC thermistor according to any one of claims 1-4, characterized in that, Includes the following steps: The semiconductor agent was mixed with nano-alumina powder and then coated and modified to obtain a coated semiconductor agent. The remaining raw materials are weighed and mixed with the coated semiconductor agent by wet ball milling and then dried to obtain ceramic material; The ceramic material is pre-calcined at 1160℃~1200℃ for 3.5h~4.5h, and then pulverized to obtain pre-calcined material; Manganese nitrate, glass powder, and rare earth oxides are dispersed in ethanol to prepare a coating solution, and the pre-calcined material is coated with the coating solution. After drying and heat treatment, the modified pre-calcined material is obtained. The modified precalcined material is mixed with a dispersant and a defoamer to form a slurry; The slurry is mixed with a binder and a plasticizer, and then subjected to spray granulation, tableting and calcination in sequence to obtain ceramic sheets. Nickel and silver layers are prepared on the surface of the ceramic sheet by sputtering and printing, respectively, to obtain a power-consuming frequency conversion starting PTC thermistor.

6. The preparation method according to claim 5, characterized in that, The mass of the dispersant is 0.08% to 0.12% of the pre-calcined material; The defoamer is 0.002% to 0.003% of the pre-calcined material by mass. The adhesive comprises 15% to 18% of the slurry by mass; The plasticizer is 0.6% to 1.2% of the slurry by mass.

7. The preparation method according to claim 5, characterized in that, The process of coating and modifying a semiconductor agent by mixing it with nano-alumina powder includes: The semiconductor agent is mixed with 0.05wt%~0.08wt% of nano-alumina powder and processed by air jet mill at a speed of 25000rpm~30000rpm for 12min~18min.

8. The preparation method according to claim 5, characterized in that, The concentration of manganese nitrate in the coating solution is 0.1wt%~0.3wt%, the concentration of glass powder is 0.05wt%~0.15wt%, and the concentration of rare earth oxides is 0.02wt%~0.08wt%. The drying heat treatment includes drying the coated powder at 80℃~120℃, and then heat-treating it at 600℃~800℃ for 1h~2h.

9. The preparation method according to claim 5, characterized in that, The calcination process includes the following steps: Heat to 600℃~700℃ at a rate of 2℃ / min~3℃ / min, and hold for 60min~90min; Introduce a nitrogen-oxygen mixed atmosphere with an oxygen content of 1% to 5%, and raise the temperature to 1150℃ to 1250℃ at a rate of 4℃ / min to 5℃ / min, and hold for 30min to 60min. Switch to pure oxygen or air with an oxygen content of 10%~21%, and heat to a peak temperature of 1320℃~1350℃ at a rate of 3℃ / min~4℃ / min, and hold for 30min~50min. Cool to 900°C at a rate of 3°C / min to 5°C / min, and then cool to room temperature in the furnace.

10. The preparation method according to claim 5, characterized in that, The thickness of the nickel layer is 0.4 μm to 0.6 μm, and the thickness of the silver layer is 3 μm to 8 μm.

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