Low-temperature sintering SnO2-based pressure-sensitive ceramic material and preparation method thereof

Abstract

The present application relates to a kind of low-temperature sintering SnO2-based pressure-sensitive ceramic material and its preparation method.The material is composed of SnO2, Zn2SnO4 and B4C powder, the molar ratio of SnO2 powder and Zn2SnO4 powder is 1:(0.2-0.5), and the molar addition amount of B4C powder is 0.05-0.3% of the sum of SnO2 powder and Zn2SnO4 powder.By traditional ceramic preparation process, a kind of low-temperature sintering SnO2-based pressure-sensitive ceramic material can be obtained.The low-temperature sintering SnO2-based pressure-sensitive ceramic material prepared by the present application has lower sintering temperature, more excellent electrical properties and simpler process compared with existing SnO2-based pressure-sensitive ceramic.

Description

Technical Field

[0001] This invention relates to a ceramic material in the field of inorganic non-metals, specifically to a low-temperature sintered SnO2-based varistor ceramic and its preparation method. Background Technology

[0002] Varistors are an important high-tech functional material whose resistance changes with the applied voltage. Varistors made from this material exhibit high resistance within a certain voltage range. When the applied voltage exceeds this range, the varistor's resistance decreases rapidly, and the current flowing through it increases exponentially, thus suppressing voltage pulses. This non-linear relationship between current and voltage is a typical characteristic of varistors. Currently, varistors are widely used in various overvoltage protection and voltage regulation circuits.

[0003] Among various varistor ceramics, SnO2-based varistor ceramics are single-phase materials with good stability and wide applications. SnO2-Zn2SnO4 composite varistor ceramics, in particular, can be obtained through traditional processes without any doping, resulting in dense SnO2-Zn2SnO4 composite ceramics. These composite ceramics possess both varistor-sensitive and dielectric properties. However, the sintering temperature of current SnO2-Zn2SnO4 composite varistor ceramics is relatively high, approximately 1300–1400℃, as shown in CN 102643087 A (A SnO2-Zn2SnO4 Composite Varistor Ceramics and Preparation Method), which uses a sintering temperature of 1300℃, and the resulting varistor ceramics have a relatively small nonlinear coefficient. Therefore, exploring a low-temperature sintering SnO2-Zn2SnO4-based varistor ceramic material and its preparation method is of great significance for SnO2-based varistor ceramics. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature sintered SnO2-based varistor ceramic material and its preparation method. This low-temperature sintered SnO2-based varistor ceramic has a high dielectric constant and a low leakage current.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing a low-temperature sintered SnO2-based varistor ceramic material, characterized by comprising the following steps:

[0007] (1) SnO2 powder, Zn2SnO4 powder and B4C powder are mixed in proportion, then ball-milled and dried to obtain a mixture;

[0008] The molar ratio of SnO2 powder to Zn2SnO4 powder is 1:(0.2-0.5), and the molar addition amount of B4C powder is 0.05-0.3% of the sum of SnO2 powder and Zn2SnO4 powder.

[0009] (2) Add a binder to the mixture obtained in step (1) to granulate and sieve to obtain granular material, press it into green sheet, remove the glue, and sinter to obtain SnO2-based pressure-sensitive ceramic material.

[0010] The sintering temperature is 1100–1200℃.

[0011] Preferably, the molar amount of B4C powder added in step (1) is 0.1±0.05% of the sum of SnO2 powder and Zn2SnO4 powder, and the molar ratio of SnO2 powder to Zn2SnO4 powder is 1:0.3; the sintering temperature in step (2) is 1150±20℃.

[0012] Preferably, in step (1), the mass ratio of powder, balls, and alcohol in the ball mill is 1:2:1, the rotation speed is 120±20 rpm, and the ball milling time is 12±2 h.

[0013] Preferably, the drying temperature in step (1) is 100-150°C and the drying time is 7-9 hours.

[0014] Preferably, the binder in step (2) is a polyvinyl alcohol solution, the amount of polyvinyl alcohol solution added is 10% to 15% of the weight of the dry powder, and the sieving is done using an 80-mesh sieve.

[0015] Preferably, the glue removal in step (2) refers to keeping the product at 600±50℃ for 2±0.5h.

[0016] Preferably, the sintering heating rate in step (2) is 3±0.5℃ / min, and the temperature is maintained for 2±0.5h before cooling.

[0017] Preferably, the Zn2SnO4 powder is prepared by mixing SnO2 and ZnO in a molar ratio of 1:2, followed by ball milling, drying, and calcination to obtain Zn2SnO4 powder.

[0018] Preferably, the ball milling speed is 120±20 rpm and the time is 12±2 h; the drying temperature is 110±10℃; and the calcination temperature is 1400±100℃ and the time is 7±1 h.

[0019] The SnO2-based varistor ceramic material prepared by the method described in this invention.

[0020] The advancement of this invention compared to the prior art lies in:

[0021] (1) Reduce sintering temperature: By adding B4C as a sintering aid, the present invention can reduce the sintering temperature of the SnO2-Zn2SnO4 system varistor ceramic to 1150℃, thereby reducing the energy consumption required for production.

[0022] (2) Improved varistor characteristics: By adjusting the amount of B4C added, this invention effectively reduces the leakage current and varistor voltage of the material and improves the nonlinear coefficient, thereby improving the varistor characteristics of the material, which is suitable for various overvoltage protection and voltage regulation circuits. Attached Figure Description

[0023] Figure 1 The nonlinear coefficients are those of the low-temperature sintered SnO2-based varistors prepared in Examples 1-5 of this invention.

[0024] Figure 2 The nonlinear coefficients and varistor voltages of the low-temperature sintered SnO2-based varistor ceramics prepared in Examples 1-5 of this invention are shown.

[0025] Figure 3 The leakage current and relative permittivity of the low-temperature sintered SnO2-based varistors prepared in Examples 1-5 of this invention are shown. Detailed Implementation

[0026] The present invention will be further described in conjunction with the following embodiments. In the embodiments of the present invention, SnO2, Zn2SnO4, and B4C are used as raw materials to prepare ceramic components through a solid-state synthesis process. The following embodiments are preferred examples conforming to the technology of the present invention and do not represent the limitation thereof.

[0027] Example 1

[0028] In this embodiment, the preparation method of low-temperature sintered SnO2-based varistor ceramic material includes the following steps:

[0029] A low-temperature sintered SnO2-based varistor ceramic material is prepared by using raw materials consisting of 1 mol SnO2 powder, 0.3 mol Zn2SnO4 powder, and x% mol B4C powder, where x = 0.

[0030] (1) Preparation of Zn2SnO4 powder: SnO2 and ZnO were mixed in a molar ratio of 1:2 and loaded into a nylon ball mill jar. Then alcohol was added and the mixture was ball milled at 120 rpm for 12 hours to obtain a slurry.

[0031] After the ball mill slurry is dried at 110℃, it is poured into a mortar and ground into powder. Then it is sent into a muffle furnace and calcined at 1400℃ for 7 hours. After that, it is naturally cooled to room temperature to obtain Zn2SnO4 powder for later use.

[0032] (2) Weigh out the analytical chemical reagent SnO2 and the Zn2SnO4 powder prepared in step (1) according to the proportions;

[0033] The molar ratio of each raw material is: 1 mol SnO2 powder : 0.3 mol Zn2SnO4 powder;

[0034] (3) Mix the SnO2 and Zn2SnO4 prepared in step (2) and then ball mill them to obtain a slurry; In this step (3), a planetary ball mill is used to ball mill the prepared raw materials. The weight ratio of the raw materials to be ball milled, the balls used, and the alcohol used is raw materials: balls: alcohol = 1:2:1. The ball milling is carried out for 12 hours at a speed of 120 rpm.

[0035] (4) Dry the slurry obtained in step (3) in an oven to obtain a mixture;

[0036] In this step (4), the drying temperature is 100-120℃ and the drying time is 7-9 hours;

[0037] (5) Add a binder to the mixed powder, granulate and sieve to obtain granular material;

[0038] In this step (5), the binder is a polyvinyl alcohol solution with a weight percentage concentration of 10%. The weight of the added polyvinyl alcohol solution is 12% of the weight of the dry powder. The granulated powder is sieved using an 80-mesh sieve.

[0039] (6) Press the granular material obtained in step (5) into green sheets;

[0040] In step (6), the powder tablets are pressed into green sheets with a diameter of 14 mm and a thickness of 1.0 mm under a pressure of 5 MPa using a powder tablet press, and then set aside.

[0041] (7) Place the green sheet into the sintering furnace and keep it at 600°C for 2 hours to allow the binder to be discharged from the green sheet.

[0042] (8) Place the blank after debinding in step (7) into a crucible and sinter it in a muffle furnace. The heating rate is 3℃ / min, the sintering temperature is 1150℃, the holding time is 2 hours, and then the blank is cooled with the furnace.

[0043] (9) Polish the ceramic surface obtained by sintering in step (8) until it is smooth, clean it with ultrasonic cleaning, and then print electrodes on both sides of the material by screen printing to obtain the required ceramic resistor.

[0044] Example 2

[0045] In this embodiment, the preparation method of low-temperature sintered SnO2-based varistor ceramic material includes the following steps:

[0046] A low-temperature sintered SnO2-based varistor ceramic material is prepared by using raw materials consisting of 1 mol SnO2 powder, 0.3 mol Zn2SnO4 powder, and x% mol B4C powder, where x = 0.05.

[0047] (1) Preparation of Zn2SnO4 powder: SnO2 and ZnO were mixed in a molar ratio of 1:2 and loaded into a nylon ball mill jar. Then alcohol was added and the mixture was ball milled at 120 rpm for 12 hours to obtain a slurry.

[0048] After the ball mill slurry is dried at 110℃, it is poured into a mortar and ground into powder. Then it is sent into a muffle furnace and calcined at 1400℃ for 7 hours. After that, it is naturally cooled to room temperature to obtain Zn2SnO4 powder for later use.

[0049] (2) Weigh out the analytical chemical reagents SnO2, B4C and Zn2SnO4 powder prepared in step (1) according to the proportions;

[0050] The molar ratio of each raw material is: 1 mol SnO2 powder : 0.3 mol Zn2SnO4 powder : 0.05% mol B4C powder;

[0051] (3) Mix SnO2, B4C and Zn2SnO4 prepared in step (2) and then ball mill them to obtain a slurry;

[0052] In this step (3), a planetary ball mill is used to ball mill the prepared raw materials. The weight ratio of the raw materials to be ball milled, the balls used, and the alcohol used is raw materials: balls: alcohol = 1:2:1. The ball milling is carried out for 12 hours at a speed of 120 rpm.

[0053] (4) Dry the slurry obtained in step (3) in an oven to obtain a mixture;

[0054] In this step (4), the drying temperature is 100-120℃ and the drying time is 7-9 hours;

[0055] (5) Add a binder to the mixed powder, granulate and sieve to obtain granular material;

[0056] In this step (5), the binder is a polyvinyl alcohol solution with a weight percentage concentration of 10%. The weight of the added polyvinyl alcohol solution is 12% of the weight of the dry powder. The granulated powder is sieved using an 80-mesh sieve.

[0057] (6) Press the granular material obtained in step (5) into green sheets;

[0058] In step (6), the powder tablets are pressed into green sheets with a diameter of 14 mm and a thickness of 1.0 mm under a pressure of 5 MPa using a powder tablet press, and then set aside.

[0059] (7) Place the green sheet into the sintering furnace and keep it at 600°C for 2 hours to allow the binder to be discharged from the green sheet.

[0060] (8) Place the blank after debinding in step (7) into a crucible and sinter it in a muffle furnace. The heating rate is 3℃ / min, the sintering temperature is 1150℃, the holding time is 2 hours, and then the blank is cooled with the furnace.

[0061] (9) Polish the ceramic surface obtained by sintering in step (8) until it is smooth, clean it with ultrasonic cleaning, and then print electrodes on both sides of the material by screen printing to obtain the required ceramic resistor.

[0062] Example 3

[0063] In this embodiment, the preparation method of low-temperature sintered SnO2-based varistor ceramic material includes the following steps:

[0064] A low-temperature sintered SnO2-Zn2SnO4-B4C composite varistor ceramic material is prepared by using raw materials consisting of 1 mol SnO2 powder, 0.3 mol Zn2SnO4 powder and x% mol B4C powder, where x = 0.1.

[0065] (1) Preparation of Zn2SnO4 powder: SnO2 and ZnO were mixed in a molar ratio of 1:2 and loaded into a nylon ball mill jar. Then alcohol was added and the mixture was ball milled at 120 rpm for 12 hours to obtain a slurry.

[0066] After the ball mill slurry is dried at 110℃, it is poured into a mortar and ground into powder. Then it is sent into a muffle furnace and calcined at 1400℃ for 7 hours. After that, it is naturally cooled to room temperature to obtain Zn2SnO4 powder for later use.

[0067] (2) Weigh out the analytical chemical reagents SnO2, B4C and Zn2SnO4 powder prepared in step (1) according to the proportions;

[0068] The molar ratio of each raw material is: 1 mol SnO2 powder : 0.3 mol Zn2SnO4 powder : 0.1% mol B4C powder;

[0069] (3) Mix SnO2, B4C and Zn2SnO4 prepared in step (2) and then ball mill them to obtain a slurry;

[0070] In this step (3), a planetary ball mill is used to ball mill the prepared raw materials. The weight ratio of the raw materials to be ball milled, the balls used, and the alcohol used is raw materials: balls: alcohol = 1:2:1. The ball milling is carried out for 12 hours at a speed of 120 rpm.

[0071] (4) Dry the slurry obtained in step (3) in an oven to obtain a mixture;

[0072] In this step (4), the drying temperature is 100-120℃ and the drying time is 7-9 hours;

[0073] (5) Add a binder to the mixed powder, granulate and sieve to obtain granular material;

[0074] In this step (5), the binder is a polyvinyl alcohol solution with a weight percentage concentration of 10%. The weight of the added polyvinyl alcohol solution is 12% of the weight of the dry powder. The granulated powder is sieved using an 80-mesh sieve.

[0075] (6) Press the granular material obtained in step (5) into green sheets;

[0076] In step (6), the powder tablets are pressed into green sheets with a diameter of 14 mm and a thickness of 1.0 mm under a pressure of 5 MPa using a powder tablet press, and then set aside.

[0077] (7) Place the green sheet into the sintering furnace and keep it at 600°C for 2 hours to allow the binder to be discharged from the green sheet.

[0078] (8) Place the blank after debinding in step (7) into a crucible and sinter it in a muffle furnace. The heating rate is 3℃ / min, the sintering temperature is 1150℃, the holding time is 2 hours, and then the blank is cooled with the furnace.

[0079] (9) Polish the ceramic surface obtained by sintering in step (8) until it is smooth, clean it with ultrasonic cleaning, and then print electrodes on both sides of the material by screen printing to obtain the required ceramic resistor.

[0080] Example 4

[0081] In this embodiment, the preparation method of low-temperature sintered SnO2-based varistor ceramic material includes the following steps:

[0082] A low-temperature sintered SnO2-Zn2SnO4-B4C composite varistor ceramic material is prepared by using raw materials consisting of 1 mol SnO2 powder, 0.3 mol Zn2SnO4 powder and x% mol B4C powder, where x = 0.2.

[0083] (1) Preparation of Zn2SnO4 powder: SnO2 and ZnO were mixed in a molar ratio of 1:2 and loaded into a nylon ball mill jar. Then alcohol was added and the mixture was ball milled at 120 rpm for 12 hours to obtain a slurry.

[0084] After the ball mill slurry is dried at 110℃, it is poured into a mortar and ground into powder. Then it is sent into a muffle furnace and calcined at 1400℃ for 7 hours. After that, it is naturally cooled to room temperature to obtain Zn2SnO4 powder for later use.

[0085] (2) Weigh out the analytical chemical reagents SnO2, B4C and Zn2SnO4 powder prepared in step (1) according to the proportions;

[0086] The molar ratio of each raw material is: 1 mol SnO2 powder : 0.3 mol Zn2SnO4 powder : 0.2 mol B4C powder;

[0087] (3) Mix SnO2, B4C and Zn2SnO4 prepared in step (2) and then ball mill them to obtain a slurry;

[0088] In this step (3), a planetary ball mill is used to ball mill the prepared raw materials. The weight ratio of the raw materials to be ball milled, the balls used, and the alcohol used is raw materials: balls: alcohol = 1:2:1. The ball milling is carried out for 12 hours at a speed of 120 rpm.

[0089] (4) Dry the slurry obtained in step (3) in an oven to obtain a mixture;

[0090] In this step (4), the drying temperature is 100-120℃ and the drying time is 7-9 hours;

[0091] (5) Add a binder to the mixed powder, granulate and sieve to obtain granular material;

[0092] In this step (5), the binder is a polyvinyl alcohol solution with a weight percentage concentration of 10%. The weight of the added polyvinyl alcohol solution is 12% of the weight of the dry powder. The granulated powder is sieved using an 80-mesh sieve.

[0093] (6) Press the granular material obtained in step (5) into green sheets;

[0094] In step (6), the powder tablets are pressed into green sheets with a diameter of 14 mm and a thickness of 1.0 mm under a pressure of 5 MPa using a powder tablet press, and then set aside.

[0095] (7) Place the green sheet into the sintering furnace and keep it at 600°C for 2 hours to allow the binder to be discharged from the green sheet;

[0096] (8) Place the blank after debinding in step (7) into a crucible and sinter it in a muffle furnace. The heating rate is 3℃ / min, the sintering temperature is 1150℃, the holding time is 2 hours, and the blank is cooled with the furnace.

[0097] (9) Polish the ceramic surface obtained by sintering in step (8) until it is smooth, clean it with ultrasonic cleaning, and then print electrodes on both sides of the material by screen printing to obtain the required ceramic resistor.

[0098] Example 5

[0099] In this embodiment, the preparation method of low-temperature sintered SnO2-based varistor ceramic material includes the following steps:

[0100] A low-temperature sintered SnO2-Zn2SnO4-B4C composite varistor ceramic material is prepared by using raw materials consisting of 1 mol SnO2 powder, 0.3 mol Zn2SnO4 powder and x% mol B4C powder, where x = 0.3.

[0101] (1) Preparation of Zn2SnO4 powder: SnO2 and ZnO were mixed in a molar ratio of 1:2 and loaded into a nylon ball mill jar. Then alcohol was added and the mixture was ball milled at 120 rpm for 12 hours to obtain a slurry.

[0102] After the ball mill slurry is dried at 110℃, it is poured into a mortar and ground into powder. Then it is sent into a muffle furnace and calcined at 1400℃ for 7 hours. After that, it is naturally cooled to room temperature to obtain Zn2SnO4 powder for later use.

[0103] (2) Weigh out the analytical chemical reagents SnO2, B4C and Zn2SnO4 powder prepared in step (1) according to the proportions;

[0104] The molar ratio of each raw material is: 1 mol SnO2 powder : 0.3 mol Zn2SnO4 powder : 0.3 mol B4C powder;

[0105] (3) Mix SnO2, B4C and Zn2SnO4 prepared in step (2) and then ball mill them to obtain a slurry;

[0106] In this step (3), a planetary ball mill is used to ball mill the prepared raw materials. The weight ratio of the raw materials to be ball milled, the balls used, and the alcohol used is raw materials: balls: alcohol = 1:2:1. The ball milling is carried out for 12 hours at a speed of 120 rpm.

[0107] (4) Dry the slurry obtained in step (3) in an oven to obtain a mixture;

[0108] In this step (4), the drying temperature is 100-120℃ and the drying time is 7-9 hours;

[0109] (5) Add a binder to the mixed powder, granulate and sieve to obtain granular material;

[0110] In this step (5), the binder is a polyvinyl alcohol solution with a weight percentage concentration of 10%. The weight of the added polyvinyl alcohol solution is 12% of the weight of the dry powder. The granulated powder is sieved using an 80-mesh sieve.

[0111] (6) Press the granular material obtained in step (5) into green sheets;

[0112] In step (6), the powder tablets are pressed into green sheets with a diameter of 14 mm and a thickness of 1.0 mm under a pressure of 5 MPa using a powder tablet press, and then set aside.

[0113] (7) Place the green sheet into the sintering furnace and keep it at 600°C for 2 hours to allow the binder to be discharged from the green sheet;

[0114] (8) Place the blank after debinding in step (7) into a crucible and sinter it in a muffle furnace. The heating rate is 3℃ / min, the sintering temperature is 1150℃, the holding time is 2 hours, and the blank is cooled with the furnace.

[0115] (9) Polish the ceramic surface obtained by sintering in step (8) until it is smooth, clean it with ultrasonic cleaning, and then print electrodes on both sides of the material by screen printing to obtain the required ceramic resistor.

[0116] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature sintered SnO2-based varistor ceramic material, characterized in that, Includes the following steps: (1) After mixing SnO2 powder, Zn2SnO4 powder and B4C powder in a certain proportion, the mixture is ball-milled and dried to obtain the mixture; The molar ratio of SnO2 powder to Zn2SnO4 powder is 1:0.3, and the molar amount of B4C powder added is 0.1±0.05% of the sum of SnO2 powder and Zn2SnO4 powder. (2) Add a binder to the mixture obtained in step (1) to granulate and sieve to obtain granular material, press it into green sheet, remove the binder, and sinter to obtain SnO2-based pressure-sensitive ceramic material; The sintering temperature is 1150±20℃, the heating rate is 3±0.5℃ / min, and the temperature is maintained for 2±0.5h before cooling.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of powder, balls, and alcohol in the ball mill is 1:2:1, the rotation speed is 120±20 rpm, and the ball milling time is 12±2 h.

3. The preparation method according to claim 2, characterized in that, The drying temperature in step (1) is 100~150℃ and the drying time is 7~9h.

4. The preparation method according to claim 3, characterized in that, The binder mentioned in step (2) is a polyvinyl alcohol solution, and the amount of polyvinyl alcohol solution added is 10% to 15% of the weight of the dry powder. The sieving is done using an 80-mesh sieve.

5. The preparation method according to claim 4, characterized in that, The glue removal mentioned in step (2) refers to keeping the product at 600±50℃ for 2±0.5h.

6. The preparation method according to any one of claims 3-5, characterized in that, The Zn2SnO4 powder was prepared by mixing SnO2 and ZnO in a molar ratio of 1:2, followed by ball milling, drying, and calcination to obtain Zn2SnO4 powder.

7. The preparation method according to claim 6, characterized in that, The ball milling speed is 120±20 rpm and the time is 12±2 h; the drying temperature is 110±10℃; the calcination temperature is 1400±100℃ and the time is 7±1 h.

8. SnO2-based varistor ceramic material prepared by the method according to any one of claims 1-7.

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