Dielectric and Piezoelectric Properties of 10% KF-Doped BaTiO3 Ceramics

概要

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10% KF-doped barium titanate powders, Ba0.9K0.1TiO2.9F0.1, were synthesized through a sol–gel process. The powders, calcined at 650 °C, consist of cubic crystalline particles of ${\sim}70$ nm in length; the particle size increases to ${\sim}200$ nm as the firing temperature increases to ca. 800 °C, above which F2 begins to evaporate. Dense ceramics were fabricated by the spark plasma sintering (SPS) method; the average grain size is ${\sim}2$ μm in lengths. The ceramics, well annealed at 1,000 °C in an O2 gas flow, have good dielectric and piezoelectric properties; the piezoelectric $d_{33}$ value is 230 pC/N at room temperature. At the ferroelectric Curie temperature $T_{\text{C}} = 47$ °C, the dielectric constant and loss $\tan\delta$ are 10,000 and ${<}5$% at 10 kHz, respectively. The Curie–Weiss relation holds in the fully disordered cubic and ordered rhombohedral phases, showing the second order $1:2$ relation. Below 10 kHz, large dielectric dispersion caused by a domain-wall motion appears at the temperature range of $-50$ to 107 °C. Some discussions are made for these dielectric properties of the ceramics.
2010-08-25