| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 91 === In the previous studies, the addition of Mn or Ca in the BME MLCC was used to prevent the occurrence of semiconducting and the deterioration of insulation resistance. However, the addition of anti-redaction additives would generate oxygen vacancies that would lead to low insulation resistance and poor life stability under high electric filed. Generally, Dy and Nb were doped in BaTiO3 to improve the life stability of BME MLCCs during HALT.
The raw materials (Ba0.96011Ca0.03988)(Ti0.82089Zr0.17911) O3（BCTZ）were doped with MnO and Nb2O5 to adjust Ba/Ti = 1. The samples then were added different amount of Dy2O3 and sintered at 1320℃ for 2 h in a reducing atmospheres. This investigation was to elucidate the effects of different addition of Dy2O3 in (Ba,Ca)(Ti,Zr) O3 on the microstructure and electricity properties.
At Dy concentration x = 0.001, Dy occupied B-site and resulted in increasing lattice constant. In this condition, Ti-rich phase Ba6Ti17O40 formed produced and lead to liquid phase sintering and grain growth. Therefore, the insulation resistance deteriorated due to the presence of Ti-rich phase Ba6Ti17O40 and the decrease of the volume fraction of grain boundary. Experimental results reveal the ofεmax increased with increasing grain size. At the doping level of 0.003 mol% to 0.01 mol%, Dy substituted A-site of the BCTZ and resulted in semiconducting at room temperature. During the temperature rose, Dy2Ti2O7 was formed, which suppressed grain growth due to the pinning effect. Some of the Ca ions were forced to occupy the B site, which act as acceptors and lead to increasement of lattice constant. Simultaneously, the formation of oxygen vacancies that can trap more free electrons and slow down the decrease of the insulation resistance. For sample with Doping 0.015 mol%, the lattice constant and insulation resistance become to decreased compared with 0.01mol% doped sample. It indicated that the occupational sites of some Dy ions changed from A site to B site and, correspondingly the amounts Ca ions in B-site decreased.
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