昇温速度により組織制御した半導性(Ba, Sr)TiO_3の電気特性

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Semiconducting (Ba_<0.9>Sr_<0.1>TiO_3 ceramics with 0.1mol% Sb_2O_3 and 0.05 mol% Ta_2O_5 were prepared by changing sintering temperature and heating rate. Microstructure, specific resistivity at room temperature, magnitude of PTCR effect and breakdown voltage of the obtained ceramics were investigated. Abnormal grain growth was observed from 1300℃ and became remarkable at the temperature regime between 1320℃ and 1360℃. The specific resistivity at room temperature decreased and the magnitude of PTCR effect increased with increasing the degree of abnormal grain growth. When the heating rate is increased from 180℃/h to 500℃/h at the temperature regime between 1300℃ and 1360℃, the grain size of the samples decreased from 44 μm to 18 μm. The specific resistivity at room temperature increased from 5 Ω cm to 7.5 Ω cm by decreasing average grain size. However, both the magnitude of PTCR effect and the resistivity in the grain evaluated by the complex impedance measurement were independent of the grain size. The breakdown voltage increased from 31 V/mm to 60 V/mm with decreasing the grain size from 44 μm to 18 μm. There was the linear relationship between the breakdown voltage and the reverse of the grain size, and the breakdown voltage of a grain boundary was estimated 0.78 V from the slope of this relationship. In this study, it was revealed that the heating rate is one of the critical factors for properties of (Ba, Sr)TiO_3 ceramics. Rapid heating at a proper temperature regime is a preferable condition for the ceramics with fine microstructure, which results in the improvement of their breakdown voltage without significant increase of the specific resistivity at room temperature.
社団法人日本セラミックス協会の論文
1997-05-01

昇温速度により組織制御した半導性(Ba, Sr)TiO_3の電気特性

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