화학공학소재연구정보센터
Journal of Industrial and Engineering Chemistry, Vol.12, No.4, 584-588, July, 2006
Dielectric Properties of BaTiO3 Ceramics Prepared from Powders with Bimodal Distribution
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BaTiO3 (BT) powders having bimodal distribution were synthesized successfully through a simple classical solid-state reaction route using cheap BaCO3 and TiO2 as starting materials. These powders were further processed in the form of green pellets to obtain dense BT ceramics having densities of 94 96 % after sintering in air at 1350 and 1400 °C/4 h in air. The room temperature dielectric constant (εRT) of 1500 at 1 KHz frequency was increased to 10000 at a Curie temperature (TC) 126 °C, showing a very sharp transition from a polar tetragonal to a non-polar cubic structure. The dielectric loss factor (tanδ) was 1.5%. SEM studies revealed the presence of dense microstructures having a distribution of smaller grains (size: 2 3μm) surrounded by larger grains ( 35 μm). The ferroelectric hysteresis loop measurements on these samples gave values of spontaneous polarization (Ps) of 12.0 μC/cm2, a coercive field (EC) of 2 2.5 kV/cm, and a dielectric strength (Eb) of 48.0 kV/cm. DC-resistivity as high as 1.5×109 Ω-cm was obtained in these samples. All these results are quite comparable with reported ferroelectric/dielectric data and are discussed elaborately in this paper.
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