A ceramic material formula, a zinc oxide varistor and its preparation method

Abstract

This invention discloses a ceramic material formula, a zinc oxide varistor, and its preparation method, relating to the field of sensitive electronic component manufacturing. The ceramic material formula comprises: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.3 parts Ta2O5, 0.01-0.5 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O. It also provides a varistor prepared from this ceramic material formulation and its preparation method, the preparation method including: fine grinding of the formulation material, slurry preparation, spray granulation, pressing, debinding, sintering, cleaning and drying, metallizing the terminal electrodes, lead welding, cleaning and drying, encapsulation with insulating material, and curing.

Description

Technical Field

[0001] This invention belongs to the field of sensitive electronic component manufacturing, specifically a ceramic material formula, a zinc oxide varistor, and its preparation method. Background Technology

[0002] Zinc oxide varistors are polycrystalline composite ceramic nonlinear resistors formed by high-temperature sintering of zinc oxide with various transition metal oxides. Their resistance changes with voltage. Their working principle is based on the surface state characteristics of zinc oxide grain boundaries. When the voltage rises to a certain level, the zinc oxide grain boundaries break down, forming a conductive path, thus causing a sharp drop in resistance. Due to their excellent overvoltage protection performance, they are widely used in security systems, railway and aviation signal systems, automotive electronics systems, low-voltage electrical appliances, low-voltage power distribution systems, communication power supplies, and building systems.

[0003] With the development of materials science and electronic technology, the performance of zinc oxide varistors has been continuously improved. Among these improvements, the control of zinc oxide grain boundaries and grain size are key factors affecting performance. In recent years, researchers have significantly enhanced the performance of zinc oxide varistors by adjusting formulations and sintering processes. Future research directions for zinc oxide varistors include further improving their performance and reliability, expanding their application areas, and exploring novel varistor materials. Refined fabrication and microstructure control of zinc oxide varistors are crucial technologies for improving their performance. Furthermore, with the continuous development of electronic technology, the application areas of zinc oxide varistors will become even wider, such as in new energy, intelligent manufacturing, and the Internet of Things.

[0004] Although the performance of zinc oxide varistors has improved rapidly, increasingly demanding operating environments, such as requiring higher operating temperatures (from 85℃ to 105℃, and even 125℃), pose a significant challenge to their high-temperature resistance. As is well known, the nominal voltage of zinc oxide varistors decreases with increasing temperature; the higher the temperature, the more pronounced the decrease, leading to higher premature failure rates and lower reliability. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing zinc oxide varistors have poor high-temperature resistance and low reliability at high temperatures. By adjusting the formula of the zinc oxide varistor and changing the packaging insulation material, a high-temperature resistant zinc oxide varistor with a normal operating temperature range of 85°C to 125°C is provided, thereby improving its reliability in high-temperature environments.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0007] On one hand, the present invention provides a ceramic material formula for a varistor, wherein the ceramic material formula comprises, by weight, 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.3 parts Ta2O5, 0.01-0.5 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0008] On the other hand, the present invention also provides a zinc oxide varistor made from the above-described ceramic material formula.

[0009] On the other hand, the present invention also provides a method for preparing a zinc oxide varistor, comprising the following steps:

[0010] Take the ceramic material formula raw materials according to the preset weight ratio, and finely grind the materials in the formula except for ZnO and Al(NO3)3·9H2O.

[0011] The finely ground raw materials, ZnO, Al(NO3)3·9H2O, pure water and additives were added to a container to prepare a homogeneous water-based slurry.

[0012] Zinc oxide pressure-sensitive ceramic powder was prepared by spray granulation using a homogeneous water-based slurry.

[0013] The ceramic powder is pressed into sheets, debinded, sintered, cleaned and dried, metallized terminal electrodes, pin soldered, cleaned and dried, encapsulated, and the encapsulation layer is cured.

[0014] Furthermore, the preset weight ratio is as follows: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.3 parts Ta2O5, 0.01-0.5 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0015] Furthermore, the additives include anionic dispersants and PVA.

[0016] Furthermore, the amount of the anionic dispersant and PVA used is (0.5-2) wt% of ZnO.

[0017] Furthermore, the solid content of the homogeneous water-based slurry is 45% to 65%.

[0018] Furthermore, the zinc oxide pressure-sensitive ceramic powder produced by granulation has a moisture content of 0.5-2%.

[0019] Furthermore, the varistor is encapsulated using insulating materials, including but not limited to epoxy resin, silicone resin, or silicone rubber.

[0020] Furthermore, after the encapsulation layer has cured, the process also includes testing and marking the cured varistor.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1. The ceramic material formula for varistors provided by this invention creatively introduces Ta2O5 and rare earth La2O3 into the formula by adjusting the composition and dosage of the formula, thereby optimizing the microstructure of zinc oxide varistors, making the grains more uniform, effectively improving the stability of the grain boundaries, and thus improving the various performance characteristics of the resistors made using this ceramic material.

[0023] 2. The zinc oxide varistor provided by this invention is made from the aforementioned ceramic material formula. Due to the innovative design of the ceramic material formula, the normal operating temperature of the zinc oxide varistor is increased from 85℃ to 125℃, enabling it to withstand high-temperature operation and effectively improving its reliability in high-temperature environments. The inventors conducted a comparative study on its performance under 8 / 20μs wave high-temperature loading impact test and high-temperature loading aging test, finding that the varistor with the introduction of Ta2O5 and rare earth La2O3 showed significantly improved impact resistance and high-temperature loading anti-aging performance.

[0024] The zinc oxide varistor provided by this invention has excellent performance and superior advantages. It solves the problem that existing zinc oxide varistors have poor high-temperature resistance and poor reliability at high temperatures.

[0025] 3. The method for preparing a zinc oxide varistor provided by the present invention is easy to manufacture, uses inexpensive and readily available materials, is simple to operate and easy to control, has universal applicability, and has good application prospects. Attached Figure Description

[0026] Figure 1 The image shows a scanning electron microscope (SEM) image of test sample 1 of the zinc oxide varistor prepared in Example 1.

[0027] Figure 2 The image shows a scanning electron microscope (SEM) image of sample 2, a zinc oxide varistor prepared for Comparative Example 1.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0029] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Detailed Implementation

[0030] The technical problem to be solved by the present invention is that the existing zinc oxide varistors have poor high temperature resistance and poor reliability at high temperatures.

[0031] On one hand, the present invention provides a ceramic material formula for a varistor, wherein the ceramic material formula comprises, by weight, 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.3 parts Ta2O5, 0.01-0.5 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0032] In some embodiments, the ceramic material formulation is preferably composed of the following raw materials in parts by weight: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.1 parts Ta2O5, 0.005-0.08 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0033] In some embodiments, the raw material composition includes the following parts by weight: 100 parts ZnO, 3 parts Bi2O3, 5 parts Sb2O3, 1 part MnO2, 2 parts Co2O3, 1 part Ni2O3, 1 part Cr2O3, 0.1 parts silver glass powder, 0.3 parts Ta2O5, 0.05 parts La2O3, and 0.05 parts Al(NO3)3·9H2O.

[0034] It is understood that by adjusting the composition and dosage of the formula, this invention creatively introduces Ta2O5 and rare earth La2O3 into the formula, which optimizes the microstructure of the zinc oxide varistor, making the grains more uniform and effectively improving the stability of the grain boundaries, thereby improving the various performance characteristics of the resistors made using this ceramic material.

[0035] On the other hand, the present invention also provides a zinc oxide varistor made from the above-described ceramic material formula.

[0036] It is understood that the zinc oxide varistor provided by this invention is made from the aforementioned ceramic material formula. Due to the innovative design of the ceramic material formula, the normal operating temperature of the zinc oxide varistor is increased from 85℃ to 125℃, enabling it to withstand high temperatures and effectively improving its reliability in high-temperature environments. The inventors conducted comparative high-temperature loading impact tests and high-temperature loading aging tests on it with an 8 / 20μs wave, finding that the varistor with the introduction of Ta2O5 and rare earth La2O3 showed significantly improved impact resistance and high-temperature loading anti-aging performance. It exhibits excellent performance and superior advantages. It solves the problem of poor high-temperature resistance and reliability of existing zinc oxide varistors at high temperatures.

[0037] On the other hand, the present invention also provides a method for preparing a zinc oxide varistor, comprising the following steps:

[0038] Take the ceramic material formula raw materials according to the preset weight ratio, and finely grind the materials in the formula except for ZnO and Al(NO3)3·9H2O.

[0039] The finely ground raw materials, ZnO, Al(NO3)3·9H2O, pure water and additives were added to a container to prepare a homogeneous water-based slurry.

[0040] Zinc oxide pressure-sensitive ceramic powder was prepared by spray granulation using a homogeneous water-based slurry.

[0041] The ceramic powder is pressed into sheets, debinded, sintered, cleaned and dried, metallized terminal electrodes, pin soldered, cleaned and dried, encapsulated, and the encapsulation layer is cured.

[0042] It is understood that the method for preparing a zinc oxide varistor provided by the present invention is easy to manufacture, uses inexpensive and readily available materials, is simple to operate and easy to control, has universal applicability, and has good application prospects.

[0043] In some embodiments of the present invention, the preset weight ratio is: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.3 parts Ta2O5, 0.01-0.5 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0044] In some embodiments, the preset weight ratio is preferably 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.1 parts Ta2O5, 0.005-0.08 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

[0045] In some embodiments of the present invention, the additives include anionic dispersants and PVA. Specifically, ammonium polyacrylate can be selected as the anionic dispersant.

[0046] In some embodiments of the present invention, the amount of the anionic dispersant and PVA is (0.5-2) wt% of ZnO.

[0047] In some embodiments of the present invention, the solid content of the homogeneous water-based slurry is 45% to 65%.

[0048] In some embodiments of the present invention, the zinc oxide pressure-sensitive ceramic powder prepared by granulation has a moisture content of 0.5-2%.

[0049] In some embodiments of the present invention, the varistor is encapsulated with insulating materials, including but not limited to epoxy resin, silicone resin or silicone rubber.

[0050] In some embodiments of the present invention, after the encapsulation layer has cured, the process further includes testing and marking the cured varistor. Specifically, the testing and marking involves performing parameter tests on the cured varistor, removing unqualified ones, and marking the qualified ones with trademarks, specifications, and certification marks.

[0051] In some embodiments of the present invention, the materials in the formula other than ZnO and Al(NO3)3·9H2O are finely ground. The fine grinding equipment adopts an advanced horizontal sand mill, and the grinding media is high-purity wear-resistant zirconia balls with a diameter of 0.3 to 1.5 mm. The formula materials, pure water, and zirconia balls are mixed in a mass ratio of 1:0.8:1, and the grinding time is 0.5 to 3 hours.

[0052] Spray granulation refers to the process of using a centrifugal spray granulation dryer with an inlet temperature of 230–280°C and an outlet temperature of 85–125°C to process the above-mentioned homogeneous water-based slurry into zinc oxide pressure-sensitive ceramic powder with a moisture content of 0.5–2%.

[0053] Pressing refers to using a powder forming machine to press the above-mentioned pressure-sensitive ceramic powder into a blank with a suitable density.

[0054] Debinding refers to the process of neatly arranging the above-mentioned blanks in a stainless steel mesh frame and slowly removing the moisture, dispersant, PVA and other organic materials from the blanks through a tunnel debinding furnace at a temperature of 200-750℃.

[0055] Sintering refers to the process of neatly and regularly placing the debinded green bodies into a high-temperature firing sagger. The sagger can be made of corundum or corundum-mullite. The green bodies are sintered into polycrystalline composite zinc oxide pressure-sensitive ceramic sheets through a high-temperature tunnel sintering furnace, undergoing heating, temperature control, and cooling processes. The temperature control ranges from 1050 to 1250℃, and the holding time is 2 to 9 hours.

[0056] Cleaning and drying refers to the process of cleaning the surface of the sintered pressure-sensitive ceramic sheets using an ultrasonic cleaner with an organic cleaning agent, followed by drying in an oven or chain tunnel furnace. The drying temperature is 100–200℃.

[0057] Metallized terminal electrodes refer to the process of screen printing or spraying silver paste containing 65-80% silver onto the two end faces of the cleaned and dried varistor ceramic sheet, drying it, and then reducing the silver paste to silver in a tunnel silver-firing furnace. The reduction temperature is 520-680℃, and the time is 10-30 minutes.

[0058] Lead soldering refers to the process of soldering conductive leads onto the varistor ceramic sheet with the metallized terminal electrodes.

[0059] Cleaning, drying, encapsulation, and curing the encapsulation layer refers to the process of cleaning the varistor with the conductive pins soldered on using an organic cleaning agent in an ultrasonic cleaner, drying it, encapsulating it with insulating material, and finally curing the encapsulation layer at a suitable temperature.

[0060] Testing and marking refer to the process of testing the parameters of the pre-encapsulated and cured varistors, removing the unqualified ones, and marking the qualified ones with trademarks, specifications, and certification marks.

[0061] Example 1:

[0062] This embodiment provides a zinc oxide varistor, whose ceramic material formula consists of the following raw materials in weight percentage: 100 parts ZnO, 3.6 parts Bi2O3, 5.5 parts Sb2O3, 0.5 parts MnO2, 2.4 parts Co2O3, 1.5 parts Ni2O3, 0.2 parts Cr2O3, 0.1 parts silver glass powder, 0.02 parts Ta2O5, 0.03 parts La2O3, and 0.008 parts Al(NO3)3·9H2O.

[0063] The specific implementation steps are as follows:

[0064] (1) Weighing of ingredients

[0065] Weigh the materials in the above formula, except for ZnO and Al(NO3)3·9H2O, according to the proportions.

[0066] (2) Finely grind the ingredients.

[0067] Add the weighed formula material from (1) to a horizontal sand mill for grinding. High-purity wear-resistant zirconia balls are used as the grinding media. The diameter of the balls is selected as 0.3-1.5 mm. Mix the formula material, pure water and zirconia balls in a mass ratio of 1:0.8:1 and grind for 1 hour.

[0068] (3) Slurry preparation

[0069] The ZnO, Al(NO3)3·9H2O, finely ground formulation materials, pure water, anionic dispersant ammonium polyacrylate, and PVA from the above formula were added to a dispersion tank and stirred at high speed for 180 minutes to finally produce a homogeneous water-based slurry with a solid content of 50%. The amount of anionic dispersant used was 0.6 wt% of ZnO, and the amount of PVA used was 0.5 wt% of ZnO.

[0070] (4) Spray granulation

[0071] The slurry in (3) is pumped into a low-speed mixing tank and then piped into the top of a centrifugal spray granulation dryer to produce zinc oxide pressure-sensitive ceramic powder with a moisture content of 0.5-2%.

[0072] (5) Tableting

[0073] The zinc oxide pressure-sensitive ceramic powder in (4) was pressed into a blank with a model number of φ23-681K and a density of 3.2 g / cm³ using a powder molding machine. 3 .

[0074] (6) De-glue

[0075] The blanks in (5) are neatly arranged in a stainless steel mesh frame and slowly removed by passing them through a tunnel debinding furnace at a temperature of 200-750°C, removing moisture, dispersant, PVA and other organic materials.

[0076] (7) Sintering

[0077] The degummed blanks from step (6) are neatly and regularly placed in a high-temperature firing sagger and sintered in a high-temperature tunnel sintering furnace through a process of heating, maintaining a constant temperature, and cooling. The blanks are then sintered into polycrystalline composite zinc oxide pressure-sensitive ceramic sheets. The constant temperature is between 1050 and 1250°C, and the holding time is between 2 and 9 hours.

[0078] (8) Cleaning, drying, and metallizing the terminal electrodes

[0079] The pressure-sensitive ceramic sheet from step (7) is placed in an ultrasonic cleaner with an organic cleaning agent to clean its surface. It is then dried in an oven at a temperature of 100–200°C. A silver paste containing 75% silver is then screen-printed onto both ends of the pressure-sensitive ceramic sheet. After drying, the silver paste is reduced to silver in a tunnel silver-firing furnace at a temperature of 520–680°C for 10–30 minutes.

[0080] (9) Pin soldering

[0081] The varistor ceramic plate with metallized terminal electrode in (8) is soldered with conductive pins.

[0082] (10) Cleaning, drying, insulation material encapsulation, and curing

[0083] The varistor silver sheet with conductive pins soldered on in (9) was cleaned in an ultrasonic cleaner with an organic cleaning agent and dried in an oven. Then it was encapsulated with silicone rubber and the encapsulation layer was cured at 25°C. This is how the zinc oxide varistor test sample 1 was made.

[0084] Comparative Example 1:

[0085] In this comparative example, a zinc oxide varistor is provided, the ceramic material of which is composed of the following raw materials by weight percentage:

[0086] 100 parts ZnO, 3.6 parts Bi₂O₃, 5.5 parts Sb₂O₃, 0.5 parts MnO₂, 2.4 parts Co₂O₃, 1.5 parts Ni₂O₃, 0.2 parts Cr₂O₃, 0.1 parts silver glass powder, 0.008 parts Al(NO₃)₃·9H₂O. (Ta₂O₅ and La₂O₃ were not added.)

[0087] The specific implementation steps are as follows:

[0088] (1) Weighing of ingredients

[0089] Weigh the materials in the above formula, except for ZnO and Al(NO3)3·9H2O, according to the proportions.

[0090] (2) Finely grind the ingredients.

[0091] The weighed ingredients from step (1) were added to a horizontal sand mill for grinding. High-purity, wear-resistant zirconia balls with a diameter of 0.3–1.5 mm were used as the grinding media. The ingredients, pure water, and zirconia balls were mixed in a mass ratio of 1:0.8:1, and the grinding time was 1 hour. (Same as Example 1)

[0092] (3) Slurry preparation

[0093] The ZnO, Al(NO3)3·9H2O, finely ground formulation materials, pure water, anionic dispersant ammonium polyacrylate, and PVA from the above formula were added to a dispersion tank and stirred at high speed for 180 minutes to finally produce a homogeneous water-based slurry with a solid content of 50%. The amount of anionic dispersant used was 0.6 wt% of ZnO, and the amount of PVA used was 0.5 wt% of ZnO. (Same as Example 1)

[0094] (4) Spray granulation

[0095] The slurry from (3) is pumped into a low-speed mixing tank, and then piped into the top of a centrifugal spray granulation dryer to produce zinc oxide pressure-sensitive ceramic powder with a moisture content of 0.5-2%. (Same as Example 1)

[0096] (5) Tableting

[0097] The zinc oxide pressure-sensitive ceramic powder in (4) was pressed into a blank with a model number of φ23-681K and a density of 3.2 g / cm³ using a powder molding machine. 3 (Same as Example 1)

[0098] (6) De-glue

[0099] The green bodies from step (5) are neatly arranged in a stainless steel mesh frame and then slowly expelled from the green bodies, along with moisture, dispersant, PVA, and other organic materials, through a tunnel debinding furnace at a temperature of 200–750°C. (Same as Example 1)

[0100] (7) Sintering

[0101] The debonded green bodies from step (6) are neatly and regularly placed in a high-temperature firing sagger and sintered in a high-temperature tunnel sintering furnace through a process of heating, maintaining a constant temperature, and cooling to form polycrystalline composite zinc oxide pressure-sensitive ceramic sheets. The constant temperature is between 1050 and 1250°C, and the holding time is between 2 and 9 hours. (Same as in Example 1)

[0102] (8) Cleaning, drying, and metallizing the terminal electrodes

[0103] The pressure-sensitive ceramic sheet from step (7) was placed in an ultrasonic cleaner with an organic cleaning agent to clean its surface. It was then dried in an oven at 100–200°C. Next, a silver paste containing 75% silver was screen-printed onto both ends of the sheet. After drying, the silver paste was reduced to silver in a tunnel silver-firing furnace at 520–680°C for 10–30 minutes. (Same as Example 1)

[0104] (9) Pin soldering

[0105] The varistor ceramic plate with the metallized terminal electrode in (8) is soldered with conductive pins. (Same as in Example 1)

[0106] (10) Cleaning, drying, insulation material encapsulation, and curing

[0107] The varistor silver sheet with conductive pins soldered on in (9) was cleaned with an organic cleaning agent in an ultrasonic cleaner and dried in an oven. Then it was encapsulated with silicone rubber and the encapsulation layer was cured at 25°C (same as in Example 1). This is how the zinc oxide varistor test sample 2 was made.

[0108] That is, the preparation method of Comparative Example 1 is the same as that of Example 1, but the formulation is different.

[0109] Comparative Example 2:

[0110] In this comparative example, a zinc oxide varistor has a ceramic material formulation composed of the following raw materials by weight percentage:

[0111] 100 parts ZnO, 3.6 parts Bi₂O₃, 5.5 parts Sb₂O₃, 0.5 parts MnO₂, 2.4 parts Co₂O₃, 1.5 parts Ni₂O₃, 0.2 parts Cr₂O₃, 0.1 parts silver glass powder, 0.02 parts Ta₂O₅, 0.03 parts La₂O₃, 0.008 parts Al(NO₃)₃·9H₂O. (Same as Example 1)

[0112] The specific implementation steps are as follows:

[0113] (1) Weighing of ingredients

[0114] Weigh all materials in the above formula except for ZnO and Al(NO3)3·9H2O according to the specified proportions. (Same as Example 1)

[0115] (2) Finely grind the ingredients.

[0116] The weighed ingredients from step (1) were added to a horizontal sand mill for grinding. High-purity, wear-resistant zirconia balls with a diameter of 0.3–1.5 mm were used as the grinding media. The ingredients, pure water, and zirconia balls were mixed in a mass ratio of 1:0.8:1, and the grinding time was 1 hour. (Same as Example 1)

[0117] (3) Slurry preparation

[0118] The ZnO, Al(NO3)3·9H2O, finely ground formulation materials, pure water, anionic dispersant ammonium polyacrylate, and PVA from the above formula were added to a dispersion tank and stirred at high speed for 180 minutes to finally produce a homogeneous water-based slurry with a solid content of 50%. The amount of anionic dispersant used was 0.6 wt% of ZnO, and the amount of PVA used was 0.5 wt% of ZnO. (Same as Example 1)

[0119] (4) Spray granulation

[0120] The slurry from (3) is pumped into a low-speed mixing tank, and then piped into the top of a centrifugal spray granulation dryer to produce zinc oxide pressure-sensitive ceramic powder with a moisture content of 0.5-2%. (Same as Example 1)

[0121] (5) Tableting

[0122] The zinc oxide pressure-sensitive ceramic powder in (4) was pressed into a blank with the model number φ23-681K using a powder molding machine, with a density of 3.2 g / cm3. (Same as Example 1)

[0123] (6) De-glue

[0124] The green bodies from step (5) are neatly arranged in a stainless steel mesh frame and then slowly expelled from the green bodies, along with moisture, dispersant, PVA, and other organic materials, through a tunnel debinding furnace at a temperature of 200–750°C. (Same as Example 1)

[0125] (7) Sintering

[0126] The debonded green bodies from step (6) are neatly and regularly placed in a high-temperature firing sagger and sintered in a high-temperature tunnel sintering furnace through a process of heating, maintaining a constant temperature, and cooling to form polycrystalline composite zinc oxide pressure-sensitive ceramic sheets. The constant temperature is between 1050 and 1250°C, and the holding time is between 2 and 9 hours. (Same as in Example 1)

[0127] (8) Cleaning, drying, and metallizing the terminal electrodes

[0128] The pressure-sensitive ceramic sheet from step (7) was placed in an ultrasonic cleaner with an organic cleaning agent to clean its surface. It was then dried in an oven at 100–200°C. Next, a silver paste containing 75% silver was screen-printed onto both ends of the sheet. After drying, the silver paste was reduced to silver in a tunnel silver-firing furnace at 520–680°C for 10–30 minutes. (Same as Example 1)

[0129] (9) Pin soldering

[0130] The varistor ceramic plate with the metallized terminal electrode in (8) is soldered with conductive pins. (Same as in Example 1)

[0131] (10) Cleaning, drying, insulation material encapsulation, and curing

[0132] The varistor silver sheet with conductive pins soldered on in (9) was cleaned with an organic cleaning agent in an ultrasonic cleaner and dried in an oven. Then it was encapsulated with epoxy resin and finally the encapsulation layer was cured at 150°C. This is how the zinc oxide varistor test sample 3 was made.

[0133] Compared to Example 1, the formulation was the same, the difference being that Comparative Example 2 used epoxy resin encapsulation. Performance verification of Test Example 1:

[0134] 1.1 Test Setup

[0135] Samples 1, 2, and 3 obtained from Examples 1, 1, and 2 were subjected to an 8 / 20 μs wave impact test, an 8 / 20 μs wave high-temperature loading impact test, and a high-temperature loading aging test, respectively. The measurement results are recorded in Table 1. The measurement results are shown in the table below.

[0136]

[0137]

[0138] 1.2 Results Analysis

[0139] Please refer to Table 1. The zinc oxide varistor of Example 1 showed low rates of change under DC 560V + 10KA × 1 cycle at 125℃ and under DC 560V + 1000h, indicating that the sample in Example 1 exhibited better DC aging performance at 125℃. Comparative Example 1 showed the highest rate of change and the worst performance. Comparative Example 2, using the same formulation but a different encapsulation material, showed a lower rate of change than Comparative Example 1, but a higher rate than Example 1.

[0140] In the 8 / 20 μs surge impact performance test, the sample of Example 1 significantly outperformed the zinc oxide varistors of Comparative Example 1 and Comparative Example 2. Comparative Example 2 was superior to Comparative Example 1.

[0141] In summary, based on performance measurements, it is evident that by adjusting the composition and dosage of the formula, and creatively introducing Ta2O5 and rare earth La2O3, the microstructure of the zinc oxide varistor was optimized, resulting in more uniform grains and effectively improving the stability of grain boundaries. This, in turn, enhanced the various performance characteristics of the resistors made using this ceramic material, significantly improving the impact resistance and high-temperature loading anti-aging properties of the varistors using this formula.

[0142] Meanwhile, after optimizing the preparation method, it was found that Comparative Example 2, which used the preparation method of the present invention, exhibited superior performance compared to Comparative Example 1. Comparing Example 1 and Comparative Example 2, it is evident that encapsulation with silicone rubber can effectively improve the impact resistance and high-temperature aging resistance of the varistor.

[0143] Microstructure analysis of Experimental Example 2:

[0144] 2.1 Test Setup

[0145] Samples 1 and 2 from Example 1 and Comparative Example 1 were observed using a scanning electron microscope under the same conditions and procedures. Specific electron microscope images are shown below. Figure 1 and Figure 2 .

[0146] 2.2 Analysis of Experimental Results

[0147] Based on scanning electron microscopy observations, see [link / reference]. Figure 1 and Figure 2 The zinc oxide varistor test sample 1 prepared in Example 1 has a uniform and dense microstructure, uniform grains, and good microstructure.

[0148] In contrast, the zinc oxide varistor sample 2 prepared in Comparative Example 1 showed significantly poor uniformity and an obviously uneven grain structure.

[0149] As described above, Example 1 and Comparative Example 1 were prepared using the same method, differing only in their formulations. Therefore, it can be concluded that by adjusting the composition and dosage of the formulation, and introducing Ta2O5 and rare earth La2O3, the microstructure of the zinc oxide varistor can indeed be effectively optimized, resulting in more uniform grains and significantly improved grain boundary stability.

[0150] The results of the joint test example 1 show that the zinc oxide varistor of example 1 has better performance. It can be seen that by optimizing the ceramic material formula, the microstructure is optimized and the performance of the resistors made using the ceramic material is improved.

[0151] The above embodiments are merely one implementation of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A ceramic material formula for a varistor, characterized in that, The ceramic material formula, by weight, includes: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.1 parts Ta2O5, 0.01-0.08 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

2. A zinc oxide varistor, characterized in that, It is made from the ceramic material formulation described in claim 1.

3. A method for preparing a zinc oxide varistor according to claim 2, characterized in that, Includes the following steps: Take the ceramic material formula raw materials according to the preset weight ratio, and finely grind the materials in the formula except for ZnO and Al(NO3)3·9H2O. The finely ground raw materials, ZnO, Al(NO3)3·9H2O, pure water and additives were added to a container to prepare a homogeneous water-based slurry. Zinc oxide pressure-sensitive ceramic powder was prepared by spray granulation using a homogeneous water-based slurry. The ceramic powder is pressed into sheets, debinded, sintered, cleaned and dried, metallized terminal electrodes, pin soldered, cleaned and dried, encapsulated, and the encapsulation layer is cured.

4. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, The preset weight ratio is as follows: 100 parts ZnO, 1.5-4.5 parts Bi2O3, 2.5-6.5 parts Sb2O3, 0.2-1.5 parts MnO2, 0.3-2.5 parts Co2O3, 0.05-2 parts Ni2O3, 0.03-1.5 parts Cr2O3, 0.01-0.2 parts silver glass powder, 0.01-0.1 parts Ta2O5, 0.01-0.08 parts La2O3, and 0.005-0.1 parts Al(NO3)3·9H2O.

5. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, The additives include anionic dispersants and PVA.

6. The method for preparing a zinc oxide varistor according to claim 5, characterized in that, The amount of anionic dispersant and PVA used is (0.5~2) wt% of ZnO.

7. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, The homogeneous water-based slurry has a solid content of 45% to 65%.

8. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, The zinc oxide pressure-sensitive ceramic powder produced by granulation has a moisture content of 0.5-2%.

9. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, The varistor is encapsulated using insulating materials, including epoxy resin, silicone resin, or silicone rubber.

10. The method for preparing a zinc oxide varistor according to claim 3, characterized in that, After the encapsulation layer is cured, the process also includes testing and marking the cured varistors.

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