A ZnO linear ceramic resistive material and its preparation method

Abstract

This invention belongs to the technical field of linear ceramic resistor materials. It provides a ZnO-based linear ceramic resistor material and its preparation method. The ZnO-based linear ceramic resistor material comprises the following raw materials: ZnO, In₂O₃, MnO₂, and SrCO₃; the molar ratio of ZnO, In₂O₃, MnO₂, and SrCO₃ is 97.5:x:x:0.4–0.6:1.5–2.5; where x is 0.1–0.4. The ZnO-based linear ceramic resistor material of this invention exhibits good ohmic characteristics with a nonlinear coefficient of approximately 1.0; it also demonstrates high temperature stability with a resistance temperature coefficient of -5.36 × 10⁻⁶. ‑3 ~ -6.03×10 ‑3 / ℃; wide adjustable resistance range; resistivity of 600~30500Ω·cm, no inductance, and good overall performance.

Description

Technical Field

[0001] This invention relates to the field of linear ceramic resistor materials, and in particular to a ZnO linear ceramic resistor material and its preparation method. Background Technology

[0002] Zinc oxide has a large band gap, strong exciton binding ability, and high conductivity, and is widely used in many fields such as semiconductor resistor materials and solar energy materials. When ZnO is used as a linear resistor, its current-voltage characteristic is linear, the nonlinear coefficient is very small and close to 1, the temperature coefficient of resistance is very small, and its resistivity is also relatively large. The characteristic of ZnO linear resistors having a small or positive negative temperature coefficient of resistance makes them less affected by temperature, and they are more suitable for use in higher temperature environments than traditional linear resistors [Xu Xi, Yan Ying, Ren Xin, et al. Influence of Al2O3 content on the microstructure and electrical properties of ZnO linear ceramic resistors [J]. Journal of Ceramics, 2019, 40(03): 307-310]. At present, among all linear resistor materials, ZnO linear resistor materials are the most stable, have the best comprehensive electrical performance, and have good application prospects [Liu Jianke. Influence of doping on the resistance characteristics of zinc oxide [D]. Xi'an: Shaanxi University of Science and Technology, 2014].

[0003] Doping with a certain amount of appropriate metal oxide can improve the electrical properties of ZnO linear resistors. The oxides used for doping are generally alkaline earth metal oxides or group III and IV saturated metal oxides [Liu Guixiang, Xu Guangliang, Ma Jianjun, et al. Preparation status and research progress of high-pressure zinc oxide varistor ceramic powder [J]. China Nonmetallic Minerals Industry Guide, 2005, 5(02): 8-11]. At present, the basic formulation of ZnO linear resistors is mainly ZnO-Al2O3-MgO-SiO2 [JFZhu, JJWang, Y.Zhu, F.Wang, Major effects on microstructure and electrical properties of ZnO-based linear resistance ceramics with MgO]. changes.J.Mater.Sci.Mater.Electron.25,2273–2278(2014).], ZnO-Al2O3-MgO-TiO2-SiO2-Fe2O3[Liu Jianke, Qiao Yinan, Zhang Ruiting et al. Effect of Fe2O3 doping on linear resistance of zinc oxide[J]. Chinese Journal of the Chinese Ceramic Society, 2021,49(03):448-454], ZnO-MgO-La2O3-ZrO2[Li Shengtao, Liu Fuyi, Xu Chuanxiang. Novel ZnO ceramic linear resistance material[J]. Functional Materials, 1996,27(01):55-60.] and ZnO-Nb2O5-Y2O3[Ji Yuanming, Zhang Jincang. Study on conductivity properties of Nb2O5-doped zinc oxide ceramic[J]. Chinese Journal of Low Temperature Physics, 2004,26(01):72-75.] etc. The electrical properties of zinc oxide resistors can be improved by doping the matrix with various metals or rare earth oxides. However, the nonlinear coefficient of existing zinc oxide linear resistors rarely reaches 1.0, or modification requires doping with many different oxides. Although the electrical performance of zinc oxide linear resistors is improved, the equipment used in the preparation methods is expensive, bulky, and increases production costs. Moreover, the required raw materials are complex and difficult to prepare.

[0004] Therefore, it is of great significance to develop a low-cost ZnO linear ceramic resistive material with good nonlinear coefficient, electrical properties, and density. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a ZnO linear ceramic resistive material and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a ZnO-based linear ceramic resistive material comprising the following raw materials: ZnO, In2O3, MnO2, and SrCO3; wherein the molar ratio of ZnO, In2O3, MnO2, and SrCO3 is 97.5:x:0.45~0.6:1.90~2.05; wherein x is 0.1~0.4.

[0008] Preferably, x is 0.2, 0.3, or 0.4.

[0009] Preferably, the resistivity of the ZnO linear ceramic resistive material is 640–30300 (Ω·cm), and the nonlinear coefficient is 1.00–1.02.

[0010] Preferably, the density of the ZnO baseline linear ceramic resistive material is 92.5% to 97.0%.

[0011] The present invention also provides a method for preparing the aforementioned ZnO baseline linear ceramic resistive material, comprising the following steps:

[0012] 1) ZnO powder, In2O3 powder, MnO2 powder, SrCO3 powder and water are mixed and then ball-milled and dried in sequence to obtain raw material powder;

[0013] 2) The raw material powder and adhesive are mixed, granulated, and then pressed into a disc shape to obtain a disc-shaped material;

[0014] 3) The disc-shaped material is sequentially debinded and sintered to obtain ZnO linear ceramic resistive material. Preferably, the ball milling time in step 1) is 6-10 hours, the ball milling speed is 320-380 r / min, and the drying temperature is 80-100℃.

[0015] Preferably, the adhesive in step 2) is a polyvinyl alcohol adhesive, and the mass of the adhesive is 3-8% of the mass of the raw material powder; the pressing pressure is 185-225 MPa.

[0016] Preferably, the temperature for discharging the adhesive in step 3) is 520–670°C, and the discharging time is 1–4 hours.

[0017] Preferably, the sintering temperature in step 3) is 1250–1350°C, the sintering time is 2–6 h, and the heating rate to the sintering temperature is 2–10°C / min.

[0018] The beneficial effects of this invention include:

[0019] 1) The ZnO linear ceramic resistive material of this invention exhibits good ohmic characteristics with a nonlinear coefficient of approximately 1.0; it also demonstrates high temperature stability with a resistance temperature coefficient of -5.36 × 10⁻⁶. -3 ~-6.03×10-3 / ℃; wide adjustable resistance range; resistivity of 600~30500Ω·cm, no inductance, and good overall performance.

[0020] 2) The preparation method of the present invention has the advantages of simple process, low energy consumption, and green environmental protection. By adding a certain amount of In2O3 to the ZnO linear resistor, the present invention can not only significantly reduce the nonlinear coefficient of the ZnO linear ceramic resistor to close to 1.0, but also reduce the resistivity and temperature coefficient of resistance of the linear ceramic to a certain extent.

[0021] 3) The ZnO-based linear ceramic resistive material of this invention has high density and stable chemical properties, and can be used to prepare current circuit breakers, energy-releasing resistors, point-grounding resistors, and non-inductive measuring resistor devices, etc. It can be applied in fields such as electronic communications, computers, automotive electronics, and consumer electronics, and has broad application prospects. The ZnO-based linear ceramic resistive material of this invention provides a new matrix and a new approach for doped and modified ZnO and other linear resistors. Attached Figure Description

[0022] Figure 1 The XRD patterns of ZnO linear ceramic resistive materials prepared in Examples 1-4 are shown below. In Example 1, 0.1 mol% In2O3 is used for Example 2, 0.2 mol% In2O3 is used for Example 3, and 0.4 mol% In2O3 is used for Example 4.

[0023] Figure 2 SEM microstructure images of the ZnO linear ceramic resistive materials prepared in Examples 1-4, where a is Example 1, b is Example 2, c is Example 3, and d is Example 4;

[0024] Figure 3 The graph shows the trend of electrical properties of the ZnO linear ceramic resistive materials prepared in Examples 1 to 4. The horizontal axis represents Example 1 (0.1), Example 2 (0.2), Example 3 (0.3), and Example 4 (0.4). Detailed Implementation

[0025] This invention provides a ZnO-based linear ceramic resistive material comprising the following raw materials: ZnO, In2O3, MnO2, and SrCO3; wherein the molar ratio of ZnO, In2O3, MnO2, and SrCO3 is 97.5:x:0.45~0.6:1.90~2.05; wherein x is 0.1~0.4.

[0026] In this invention, the molar ratio of ZnO, In2O3, MnO2 and SrCO3 is preferably 97.1-97.3:0.2-0.4:0.48-0.55:1.95-2.0 (x is 0.2-0.4), more preferably 97.1-97.2:0.3-0.4:0.5:1.98 (x is 0.3-0.4), where x is preferably 0.2, 0.3 or 0.4.

[0027] In this invention, the resistivity of the ZnO linear ceramic resistive material is preferably 640 to 30300 (Ω·cm), and the nonlinear coefficient is preferably 1.00 to 1.02.

[0028] In this invention, the density of the ZnO linear ceramic resistive material is preferably 92.5% to 97.0%.

[0029] The present invention also provides a method for preparing the aforementioned ZnO baseline linear ceramic resistive material, comprising the following steps:

[0030] 1) ZnO powder, In2O3 powder, MnO2 powder, SrCO3 powder and water are mixed and then ball-milled and dried in sequence to obtain raw material powder;

[0031] 2) The raw material powder and adhesive are mixed, granulated, and then pressed into a disc shape to obtain a disc-shaped material;

[0032] 3) The disc-shaped material is sequentially debonded and sintered to obtain ZnO linear ceramic resistor material.

[0033] In this invention, the ball milling time in step 1) is preferably 6-10 hours, more preferably 7-9 hours, and even more preferably 8 hours; the ball milling speed is preferably 320-380 r / min, more preferably 340-350 r / min; the ball mill used is preferably a planetary ball mill, a sand mill, or other industrial ceramic powder mixing device, and more preferably a QM-3SP2 omnidirectional planetary ball mill produced by Nanjing Qianshang Electronic Technology Co., Ltd., an RTSM-0.5ADD laboratory sand mill produced by Shanghai Rute Electromechanical Equipment Co., Ltd., or a ZSH-0.05 ribbon conical mixer produced by Shanghai Kairi Machinery Manufacturing Co., Ltd.

[0034] In this invention, the drying temperature in step 1) is preferably 80-100°C, more preferably 85-95°C, and even more preferably 90°C; the drying process is preferably thorough drying.

[0035] In this invention, the adhesive in step 2) is preferably a polyvinyl alcohol adhesive, and the mass of the adhesive is preferably 3-8% of the mass of the raw material powder, more preferably 4-7%, and even more preferably 5-6%; the pressing pressure is preferably 185-225 MPa, and more preferably 200 MPa.

[0036] In this invention, the raw material powder does not need to be calcined; it is directly pressed, debinded, and sintered.

[0037] In this invention, the temperature for discharging adhesive in step 3) is preferably 520–670°C, more preferably 540–630°C, and even more preferably 550–610°C; the discharging time is preferably 1–4 hours, and even more preferably 2–3 hours.

[0038] In this invention, the purpose of degreasing is to remove the polyvinyl alcohol adhesive.

[0039] In this invention, the sintering temperature in step 3) is preferably 1250-1350℃, more preferably 1270-1320℃, and even more preferably 1290-1300℃; the sintering time is preferably 2-6h, more preferably 3-5h, and even more preferably 4h; the heating rate to the sintering temperature is preferably 2-10℃ / min, more preferably 3-8℃ / min, and even more preferably 5-7℃ / min.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] In this embodiment, the ball mill used is a QM-3SP2 omnidirectional planetary ball mill manufactured by Nanjing Qianshang Electronic Technology Co., Ltd.

[0042] Example 1

[0043] 97.4% ZnO powder, 0.1% In2O3 powder, 0.45% MnO2 powder, and 2.05% SrCO3 powder were placed in a ball mill jar and wet ball milled with deionized water as the medium. The amount of deionized water added was 1 / 2 of the volume of the ball mill jar. The mixture was ball milled for 6 hours (the ball mill speed was 380 r / min), and then dried in an oven at 80°C to obtain the raw material powder.

[0044] The raw material powder and polyvinyl alcohol adhesive (the mass of the polyvinyl alcohol adhesive is 3% of the mass of the raw material powder) were mixed and pressed at 185 MPa to form thin discs with a diameter of 12 mm and a thickness of 0.6 mm. The discs were then held at 520 °C for 2 hours in a muffle furnace to remove the polyvinyl alcohol adhesive. The temperature was then increased to 1250 °C at a rate of 10 °C / min and sintered at 1250 °C for 6 hours to obtain ZnO linear ceramic resistance material.

[0045] Example 2

[0046] 97.3% ZnO powder, 0.2% In2O3 powder, 0.5% MnO2 powder, and 2.0% SrCO3 powder were placed in a ball mill jar and wet ball milled with deionized water as the medium. The amount of deionized water added was 1 / 2 of the volume of the ball mill jar. The mixture was ball milled for 7 hours (the ball mill speed was 360 r / min), and then dried in an oven at 90°C to obtain the raw material powder.

[0047] The raw material powder and polyvinyl alcohol adhesive (the mass of the polyvinyl alcohol adhesive is 5% of the mass of the raw material powder) were mixed and pressed at 200 MPa to form thin discs with a diameter of 12 mm and a thickness of 0.6 mm. The discs were then held at 550 °C for 2 hours in a muffle furnace to remove the polyvinyl alcohol adhesive. The temperature was then increased to 1290 °C at a rate of 7 °C / min and held at 1290 °C for 4 hours for sintering to obtain ZnO linear ceramic resistance material.

[0048] Example 3

[0049] 97.2% ZnO powder, 0.3% In2O3 powder, 0.55% MnO2 powder, and 1.95% SrCO3 powder were placed in a ball mill jar and wet ball milled with deionized water as the medium. The amount of deionized water added was 1 / 2 of the volume of the ball mill jar. The mixture was ball milled for 9 hours (the ball mill speed was 340 r / min), and then dried in an oven at 80°C to obtain the raw material powder.

[0050] The raw material powder and polyvinyl alcohol adhesive (the mass of the polyvinyl alcohol adhesive is 6% of the mass of the raw material powder) were mixed and pressed at 225 MPa to form thin discs with a diameter of 12 mm and a thickness of 0.6 mm. The discs were then held at 570 °C for 2 hours in a muffle furnace to remove the polyvinyl alcohol adhesive. The temperature was then increased to 1320 °C at a rate of 5 °C / min and held at 1320 °C for 3 hours for sintering to obtain ZnO linear ceramic resistance material.

[0051] Example 4

[0052] ZnO powder (97.1% molar percentage), In2O3 powder (0.4% molar percentage), MnO2 powder (0.6% molar percentage), and SrCO3 powder (1.9% molar percentage) were placed in a ball mill jar. Deionized water was used as the medium for wet ball milling, and the amount of deionized water added was 1 / 2 of the volume of the ball mill jar. The mixture was ball milled for 10 hours (the ball mill speed was 320 r / min), and then dried in an oven at 80°C to obtain the raw material powder.

[0053] The raw material powder and polyvinyl alcohol adhesive (the mass of the polyvinyl alcohol adhesive is 5% of the mass of the raw material powder) were mixed and pressed at 200 MPa to form thin discs with a diameter of 12 mm and a thickness of 0.6 mm. The discs were then held at 550 °C for 2 h in a muffle furnace to remove the polyvinyl alcohol adhesive. The temperature was then increased to 1350 °C at a rate of 2 °C / min and held at 1350 °C for 2 h for sintering to obtain ZnO linear ceramic resistance material.

[0054] The ZnO linear ceramic resistive material samples from Examples 1 to 4 were coated with silver paste on both sides and then fired at 550°C for 20 minutes to obtain silver electrodes. The electrical performance was then tested and analyzed, and the results are shown in Table 1.

[0055] Table 1 Performance test results of silver electrodes prepared from ZnO baseline linear ceramic resistive materials

[0056] Example <![CDATA[ρ g / Ω·cm]]> <![CDATA[ρ gb / KΩ·cm]]> <![CDATA[φ0(eV)]]> α <![CDATA[α T (×10 -3 )]]> ρ(Ω·cm) Example 1 21.29 61.69 0.2274 1.02 -5.9 30300.00 Example 2 24.21 3.21 0.1847 1.01 -6.03 4200 Example 3 21.74 1.97 0.1654 1.00 -5.37 1005.00 Example 4 19.31 1.45 0.1704 1.02 -5.36 640.00

[0057] The XRD patterns of the ZnO linear ceramic resistive materials prepared in Examples 1-4 are as follows: Figure 1 As shown, 0.1 mol% In2O3 is Example 1, 0.2 mol% In2O3 is Example 2, 0.3 mol% In2O3 is Example 3, and 0.4 mol% In2O3 is Example 4.

[0058] The SEM microstructure images of the ZnO linear ceramic resistive materials prepared in Examples 1-4 are shown below. Figure 2 As shown, a is Example 1, b is Example 2, c is Example 3, and d is Example 4.

[0059] The line graphs showing the electrical property trends of the ZnO baseline ceramic resistive materials prepared in Examples 1-4 are shown below. Figure 3 As shown, the horizontal axis is 0.1 for Example 1, 0.2 for Example 2, 0.3 for Example 3, and 0.4 for Example 4.

[0060] From Table 1 and Figure 1 It can be seen that the nonlinear coefficient of the resistance sample in Example 1 is close to 1, indicating good linearity, high crystallinity, and strong compactness.

[0061] Combined with Table 1 Figure 2 , Figure 3 It can be seen that as the doping amount of In2O3 increases, the cell size of the matrix continues to increase, the grain boundary barrier height first decreases and then increases slightly, the temperature coefficient of resistance and the nonlinear coefficient remain almost unchanged and remain close to 1, while the resistivity further decreases.

[0062] By examining the microstructure and electrical properties of the material, it was found that the incorporation of In₂O₃ not only coarsens the grain size, thus reducing resistivity, but also increases the nonlinear coefficient and lowers the temperature coefficient of resistance. When the molar percentage of In₂O₃ powder is 0.3%, the linear resistor prepared from ZnO-based linear ceramic resistive material exhibits the following comprehensive performance: nonlinear coefficient α = 1.0, and temperature coefficient of resistance = -5.37 × 10⁻⁶. -3 / ℃.

[0063] The ZnO linear ceramic resistive material of this invention exhibits good ohmic characteristics with a nonlinear coefficient of approximately 1.0; it also demonstrates high temperature stability with a resistance temperature coefficient of -5.36 × 10⁻⁶. -3 ~-6.03×10 -3 / ℃; wide adjustable resistance range; resistivity 600~30500Ω·cm, no inductance, and excellent overall performance. This invention provides a high-density ZnO-In2O3 baseline linear ceramic material and its devices, creating conditions for the preparation of low-cost, high-temperature-stability, wide adjustable resistance range, and inductance-free ZnO baseline linear ceramic resistors, which have broad application prospects in modern industrial production.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A ZnO-based linear ceramic resistive material, characterized in that, The preparation materials include ZnO, In2O3, MnO2 and SrCO3; the molar ratio of ZnO, In2O3, MnO2 and SrCO3 is 97.5-x:x:0.45~0.6:1.90~2.05; wherein x is 0.1~0.

4.

2. The ZnO linear ceramic resistive material according to claim 1, characterized in that, x is 0.2, 0.3, or 0.

4.

3. The ZnO linear ceramic resistive material according to claim 1 or 2, characterized in that, The resistivity of ZnO linear ceramic resistive material is 640–30300 (Ω·cm), and the nonlinear coefficient is 1.00–1.

02.

4. The ZnO baseline linear ceramic resistive material according to claim 3, characterized in that, The density of ZnO baseline ceramic resistive materials is 92.5%–97.0%.

5. The method for preparing the ZnO baseline linear ceramic resistive material according to any one of claims 1 to 4, characterized in that, It includes the following steps: 1) ZnO powder, In2O3 powder, MnO2 powder, SrCO3 powder and water are mixed and then ball-milled and dried in sequence to obtain raw material powder; 2) The raw material powder and adhesive are mixed, granulated, and then pressed into a disc shape to obtain a disc-shaped material; 3) The disc-shaped material is sequentially debonded and sintered to obtain ZnO linear ceramic resistor material.

6. The preparation method according to claim 5, characterized in that, Step 1) The ball milling time is 6 to 10 hours, and the ball milling speed is 320 to 380 r / min; the drying temperature is 80 to 100℃.

7. The preparation method according to claim 5 or 6, characterized in that, Step 2) The adhesive is a polyvinyl alcohol adhesive, and the mass of the adhesive is 3-8% of the mass of the raw material powder; the pressing pressure is 185-225 MPa.

8. The preparation method according to claim 7, characterized in that, Step 3) The temperature for discharging the adhesive is 520-670℃, and the discharging time is 1-4 hours.

9. The preparation method according to claim 8, characterized in that, Step 3) The sintering temperature is 1250-1350℃, the sintering time is 2-6h, and the heating rate to the sintering temperature is 2-10℃ / min.

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