阅读说明：本技术 一种低温烧结氧化锌压敏陶瓷及其制备方法 (Low-temperature sintered zinc oxide pressure-sensitive ceramic and preparation method thereof ) 是由 卢振亚 肖淼淼 杨凤金 于 2020-05-20 设计创作，主要内容包括：本发明公开了一种低温烧结氧化锌压敏陶瓷及其制备方法,将氧化锌、烧结助剂B<Sub>4</Sub>C和改性添加剂混合并球磨,干燥后得粉料；改性添加剂含有Bi<Sub>2</Sub>O<Sub>3</Sub>、Sb<Sub>2</Sub>O<Sub>3</Sub>、Co<Sub>3</Sub>O<Sub>4</Sub>、锰的氧化物和Ni<Sub>2</Sub>O<Sub>3</Sub>；得到的粉料加PVA胶,造粒过筛,压片排胶；于900-950℃烧结2-3h,获得黑色致密的压敏陶瓷片；再将压敏陶瓷片的两面分别涂覆银浆,升温至500℃-550℃,保温20-30分钟后冷却,得到两面均印有电极的压敏陶瓷。本发明通过采用B<Sub>4</Sub>C作为烧结助剂,将烧结温度从传统的1100-1200℃降至950℃以下的同时也保证了压敏陶瓷具备良好的综合电性能,整体工艺节能降耗,绿色环保,简便易行且可工业化推广。(The invention discloses a low-temperature sintered zinc oxide pressure-sensitive ceramic and a preparation method thereof, wherein zinc oxide and a sintering aid B are mixed 4 C, mixing the modified additive with the C, ball-milling and drying to obtain powder; the modifying additive contains Bi 2 O 3 、Sb 2 O 3 、Co 3 O 4 Oxides of manganese and Ni 2 O 3 (ii) a Adding PVA (polyvinyl alcohol) glue into the obtained powder, granulating, sieving, tabletting and discharging glue; sintering at 900-950 ℃ for 2-3h to obtain a black compact pressure-sensitive ceramic plate; and coating silver paste on two surfaces of the pressure-sensitive ceramic sheet respectively, heating to 500-550 ℃, preserving heat for 20-30 minutes, and cooling to obtain the pressure-sensitive ceramic with the electrodes printed on the two surfaces. The invention is realized by adopting B 4 The C is used as a sintering aid, the sintering temperature is reduced from the traditional 1100-plus-material 1200 ℃ to below 950 ℃, and meanwhile, the pressure-sensitive ceramic has good comprehensive electrical property, the whole process is energy-saving and consumption-reducing, green and environment-friendly, simple and feasible, and can be industrially popularized.)

1. The preparation method of the low-temperature sintered zinc oxide pressure-sensitive ceramic is characterized by comprising the following steps of:

(1) mixing zinc oxide, a sintering aid and a modification additive, ball-milling and drying to obtain powder; the sintering aid is B₄C, the modifying additive contains Bi₂O₃、Sb₂O₃、Co₃O₄Oxides of manganese and Ni₂O₃；

(2) Adding PVA glue into the obtained powder, granulating, sieving, pressing and forming, and then carrying out glue discharging treatment on the obtained ceramic green compact;

(3) sintering the ceramic blank piece after the glue is discharged, wherein the sintering temperature is 900-950 ℃, and the sintering time is 2-3 hours, so as to obtain a black compact pressure-sensitive ceramic piece;

(4) and respectively coating silver paste on two surfaces of the pressure-sensitive ceramic sheet, heating to 500-550 ℃, preserving heat for 20-30 minutes, and cooling to obtain the pressure-sensitive ceramic with the electrodes printed on the two surfaces.

2. The method according to claim 1, wherein the ZnO and Bi of step (1)₂O₃、Sb₂O₃、Co₃O₄Manganese oxide, Ni₂O₃In a molar percentage of (95.3-98.6): (0.5-1.5): (0.5-1.5): (0.2-0.5): (0.1-0.7): (0.1-0.5), and the sum of the contents of all the components is 100%; b is₄The mass ratio of C to ZnO is (0.2-1): 100.

3. the method according to claim 2, wherein the modifying additive further comprises Cr₂O₃、Al(NO₃)·9H₂O and SiO₂Said Cr being₂O₃、Al(NO₃)·9H₂O、SiO₂And ZnO in a mass ratio of (0.1-1): (0.01-0.1): (0.1-1): 100.

4. the method according to claim 3, wherein B is₄The mass ratio of C to ZnO is 0.5: 100.

5. the method as set forth in claim 1 or 2 or 3 or 4, wherein the sintering in step (3) is carried out at a rate of 4-6 ℃ per minute to a sintering temperature of 900-910 ℃ for 2.5-3 hours.

6. The method according to claim 1 or 2 or 3 or 4, wherein the PVA based adhesive in step (2) is a polyvinyl alcohol solution and is added in an amount of 10 to 12 wt% based on ZnO.

7. The preparation method according to claim 1 or 2 or 3 or 4, wherein the temperature for gel removal in step (2) is 600 ℃ and 650 ℃, and the holding time is 1-1.5 h.

8. The preparation method according to claim 1, 2, 3 or 4, wherein the powder in the step (1) is put into a ball milling tank, mixed with water and ball milled for 40-60 minutes, and the mass ratio of the powder, the balls and the water is 1.5: 1: 1; the oxide of manganese in the modified additive is Mn₃O₄Or MnO₂。

9. The production method according to claim 1 or 2 or 3 or 4, wherein the pressure for press molding in the step (3) is 80 to 100MPa, and the dwell time is 3 to 5 seconds.

10. The zinc oxide pressure sensitive ceramic prepared by the method of any one of claims 1 to 9.

Technical Field

The invention relates to a low-temperature sintered zinc oxide voltage-sensitive ceramic and a preparation method thereof, belonging to the technical field of voltage-sensitive resistor materials.

Background

ZnO varistors are widely used in electronic circuits and power systems as voltage regulation and surge protection devices due to their excellent nonlinear current-voltage characteristics and high energy absorption capability. As electronic circuits are developed toward integration and miniaturization, the corresponding protection components are also required in terms of volume, and the multilayer piezoresistors which can be used for surface mounting are greatly reduced in size.

The sintering temperature range of ZnO pressure sensitive ceramic is 1100-1200 ℃, and silver palladium alloy with high melting point is commonly used as the inner electrode at such high temperature to realize high-temperature co-firing of the inner electrode and the pressure sensitive ceramic layer. But Bi in the pressure-sensitive ceramic layer during high-temperature co-firing₂O₃And Pd in the internal electrode, so that the electrical properties of the multilayer varistor deteriorate. If the co-firing temperature, namely the sintering temperature of the pressure-sensitive ceramic can be reduced to be lower than the melting point of Ag (about 960 ℃), the pure silver electrode can be used for replacing the silver-palladium inner electrode, the electrical property deterioration is avoided, and the cost is reduced. The promotion of sintering by the addition of a low-melting sintering aid which forms a liquid phase at a lower temperature is a well-established economical and efficient method for lowering the sintering temperature, the common sintering aid being B₂O₃Boron-based frits, and the like.

The tape casting method is an important process for preparing the multilayer piezoresistor, and the traditional tape casting slurry mostly takes an organic solvent as a matrix, has the defects of toxicity and environmental pollution, so that the research of a water-based tape casting process taking an aqueous solvent as a matrix, which is green, environment-friendly, non-toxic and safe, is the main trend. When B is added to the ceramic base₂O₃When boron-based glass material is used as sintering aid, B which is soluble in water when slurry is prepared₂O₃、HBO₃And the boron-based glass material which is slightly soluble in water can react with the organic binder with hydroxyl or amino and the dispersing agent in the slurry to form a complex compound, so that the rheological property and the chemical uniformity of the slurry are influenced, and further, the preparation of the water-based casting slurry and the performance of a green film are influenced. The preparation of slurry is the first link of the tape casting process, and the adhesiveAnd the dispersant is an indispensable part in the basic composition of the slurry, so that the selection of the sintering aid with stable chemical property becomes the key for preparing the multilayer piezoresistor by adopting a water-based casting process.

In summary, on one hand, the sintering temperature is reduced, the low-temperature co-firing of the pressure-sensitive ceramic layer and the pure silver electrode is realized, and the energy is saved and the consumption is reduced; on the other hand, the multilayer chip piezoresistor can be prepared by adopting a water-based tape casting process so as to respond to the national green call. Therefore, a proper sintering aid is explored, and the method has great significance for the research of the low-temperature sintering direction of the multilayer chip zinc oxide piezoresistor.

Disclosure of Invention

The invention aims to provide a low-temperature sintered zinc oxide pressure-sensitive ceramic and a preparation method thereof, aiming at the problems of over-high sintering temperature, reaction generated when an inner electrode and a ceramic layer are co-fired and the like in the prior preparation technology of multilayer chip pressure-sensitive ceramic.

The purpose of the invention is realized by the following technical scheme:

a preparation method of low-temperature sintered zinc oxide pressure-sensitive ceramic comprises the following steps:

(1) mixing zinc oxide, sintering aid and modified additive in proportion, ball-milling and drying to obtain powder; the sintering aid is B₄C, the modifying additive contains Bi₂O₃、Sb₂O₃、Co₃O₄Oxides of manganese and Ni₂O₃；

(2) Adding PVA glue into the obtained powder, granulating, sieving, pressing and forming, and then carrying out glue discharging treatment on the obtained ceramic green compact;

(3) sintering the ceramic blank piece after the glue is discharged, wherein the sintering temperature is 900-950 ℃, and the sintering time is 2-3 hours, so as to obtain a black compact pressure-sensitive ceramic piece;

(4) and (3) coating silver paste on two surfaces of the pressure-sensitive ceramic sheet respectively by using a conventional screen printing process, heating to 500-550 ℃, preserving heat for 20-30 minutes, and cooling to obtain the pressure-sensitive ceramic with the electrodes printed on the two surfaces.

Preferably, the ZnO and Bi of step (1)₂O₃、Sb₂O₃、Co₃O₄Manganese oxide, Ni₂O₃In a molar percentage of (95.3-98.6): (0.5-1.5): (0.5-1.5): (0.2-0.5): (0.1-0.7): (0.1-0.5), and the sum of the contents of all the components is 100%; b is₄The mass ratio of C to ZnO is (0.2-1): 100.

preferably, B is₄The mass ratio of C to ZnO is 0.5: 100.

preferably, the modifying additive also contains Cr₂O₃、Al(NO₃)·9H₂O and SiO₂Said Cr being₂O₃、Al(NO₃)·9H₂O、SiO₂And ZnO in a mass ratio of (0.1-1): (0.01-0.1): (0.1-1): 100.

preferably, the sintering in step (3) is increased to the sintering temperature at a heating rate of 4-6 ℃ per minute, the sintering temperature is 900-910 ℃, and the sintering time is 2.5-3 hours.

Preferably, the PVA gel in the step (2) is a polyvinyl alcohol solution, and the addition amount of the PVA gel is 10-12 wt% of ZnO.

Preferably, the gel discharging temperature is 600-650 ℃, and the heat preservation time is 1-1.5 h.

Preferably, the powder material in the step (1) is put into a ball milling tank, water is added for mixing, and ball milling is carried out for 40-60 minutes, wherein the mass ratio of the powder material to the balls to the water is 1.5: 1: 1.

preferably, the oxide of manganese in the modifying additive is Mn₃O₄Or MnO₂。

Preferably, the pressure of the compression molding in the step (3) is 80-100MPa, and the dwell time is 3-5 seconds.

Compared with the prior art, the invention has the beneficial effects that:

the invention has simple process, adopts the traditional solid phase synthesis method and uses B₄C is used as a sintering aid to realize the low-temperature sintering of the zinc oxide pressure-sensitive ceramic, and the sintering temperature is reduced from the traditional 1100-1200 ℃ to 900-950 ℃. B is₄C has stable chemical property, does not react with other additives at normal temperature to influence the preparation of the slurry, and is oxidized and decomposed at about 600 ℃ to generate B₂O₃The glass phase is uniformly distributed in the matrix, assists the Bi-rich liquid phase to wet ZnO crystal grains, accelerates mass transfer, promotes sintering, can ensure the full development of the crystal grains while reducing the sintering temperature, and B₄The B element in C has a percentage content of up to 78%, unit B₄C converted B₂O₃The amount is high. Part B of the sintering process₂O₃The glass phase and ZnO are combined to generate a zinc borate phase, and the zinc borate phase plays a similar pinning effect with spinel, so that abnormal growth of crystal grains is prevented, and the potential gradient of the pressure sensitive ceramic is improved.

The invention combines the preparation of the multilayer chip piezoresistor by the water-based tape casting process and the low-temperature sintering, and meets the requirement of replacing the silver palladium electrode in the multilayer chip piezoresistor as a pure silver inner electrode. The prepared zinc oxide pressure-sensitive ceramic has the potential gradient between 1200-1300V/mm, the nonlinear coefficient between 20 and 30, the leakage current control about 10 muA, good comprehensive electrical property and uniform microstructure.

The invention is environment-friendly, energy-saving and consumption-reducing, and is suitable for industrial popularization and application.

Drawings

FIG. 1 is an SEM image of a zinc oxide pressure sensitive ceramic of a comparative example of the present invention.

FIG. 2 is an SEM image of a zinc oxide pressure sensitive ceramic in example 1 of the present invention.

FIG. 3 is an SEM image of a zinc oxide pressure sensitive ceramic in example 2 of the present invention.

FIG. 4 is an SEM image of a zinc oxide pressure sensitive ceramic in example 3 of the present invention.

FIG. 5 is an SEM image of a zinc oxide pressure sensitive ceramic in example 4 of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples, which are provided below, and it should be understood that the following embodiments are only for helping the skilled person to better understand the present invention, and do not limit the present invention.