退火对TiO2-Ta2O5-CaCO3陶瓷结构及压敏性能的影响

本文研究了退火对TiO2-Ta2O5-CaCO3压敏陶瓷的压敏性能的影响，采用球磨-成型-烧结的传统方法制备TiO2-Ta2O5-CaCO3压敏陶瓷，并将TiO2-Ta2O5-CaCO3压敏陶瓷在不同温度下退火，用压敏直流参数仪测试样品的非线性系数α、压敏电压EB，采用XRD、SEM和STEM分析微观结构。结果表明，适宜温度下退火适当时间，可使晶粒适当长大，并使晶粒粒度分布均匀，减少气孔和提高致密度。退火过程中，半径较大的受主离子获得动能进一步向晶界偏析，增大晶界受主态密度，从而提高非线性系数α。晶粒适当长大，晶界数量和晶界总面积减小，有助于减小压敏电压；提高致密度可减小电阻率，从而进一步减小压敏电压。当掺杂浓度为0.20mol%，烧结温度为1 350 ℃，700 ℃退火3 h的TiO2-Ta2O5-CaCO3压敏陶瓷获得最高的非线性系数和较低的压敏电压(α=8.6， EB=22.5 V?mm-1)，优于没有退火样品。

Abstract

The effect of annealing on varistor properties of TiO2-Ta2O5-CaCO3 varistor ceramics was studied. TiO2-Ta2O5-CaCO3 varistor ceramics were prepared by the traditional ball mill-molding-sintering method, then these varistor ceramics were annealed at different temperatures. The nonlinear coefficient α and varistor voltage EB of these samples were tested with varistor DC parameters and their microstructures were analyzed by XRD, SEM and STEM. The result shows that annealing at suitable temperature for appropriate time can make the grain grow up slightly, which results uniform grain sizes, less porosity and higher grain density. During annealing, the acceptor ions with larger radius obtain kinetic energy and move towards the grain boundary. The state density of acceptor increases at the grain boundary will improve the nonlinear coefficient α. The number and total area of grain boundaries decrease with grain grown properly, which is helpful to reduce the varistor voltage. At the same time, the densification of grains increases and the resistivity decreases, which further reduces the varistor voltage. When doping concentration is 0.20mol%, and sintering temperature is 1 350 ℃, TiO2-Ta2O5-CaCO3 varistor ceramic annealed at 700 ℃ for 3 h obtains the highest nonlinear coefficient and lower varistor voltage (α=8.6, EB=22.5 V?mm-1), which is better than TiO2-Ta2O5-CaCO3 varistor ceramic unannealed.

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康昆勇, 朱刚, 徐开蒙. 退火对TiO2-Ta2O5-CaCO3陶瓷结构及压敏性能的影响[J]. 人工晶体学报, 2020, 49(4): 694. KANG Kunyong, ZHU Gang, XU Kaimeng. Effect of Annealing on Structure and Varistor Properties of TiO2-Ta2O5-CaCO3 Ceramics[J]. Journal of Synthetic Crystals, 2020, 49(4): 694.

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