BaTiO_3基PTC陶瓷低阻化新途径与显微分析

NOVEL APPROACH TO LOWER ROOM TEMPERATURE RESISTIVITY OF PTC CERAMICS WITH HIGH AMPLITUDE AND THEIR MICROSTRUCTURE ANALYSIS

利用传统烧结工艺,将一定配比的BaCO_3和Pb_3O_4 2种粉料在二次配料时加入BaTiO_3煅烧料中,通过改变n(Pb)/n(Ba)的摩尔比,获得了具有应用前景的高性能正温度系数热敏电阻(PTCR)陶瓷。通过TEM观察,重点分析了n(Pb)/n(Ba)对晶界处的元素分布和晶粒上的畴结构的影响,发现n(Pb)/n(Ba)>1的样品存在着大量的90°电畴,而n(Pb)/n(Ba)<1的样品电畴发育不完善,并存在晶界第二相。结合Jonker的铁电补偿模型和Desu提出的陷阱活化能概念较好地解释了低阻化现象。阻抗谱结果很好地验证了分析结果。

A novel approach to lower the room temperature resistivity of PTC ceramics with high amplitude by adding BaCO3 and Pb3O4 powders with appropriate proportion to as-calcined BaTiO3 was introduced. The microstructure, element distribution and domain structure were revealed by the TEM analysis. It is found that there exist a great deal of 90° electrical domain in huge grain and oxygen vacancy in the grain boundary of the sample whose molar ratio n(Pb)/n(Ba)>1, while the situation in the sample whose molar ratio n(Pb)/n(Ba)<1 is just the reverse. The lowering-room resistivity phenomena are preferably interpreted with the aid of the ferroelectric compensation model developed by Jonker and the barrier activation energy model advanced by Desu. The analysis results from impedance spectrum also verify the analysis.