KTaO_3 Ceramics Prepared by the Mechanochemically Activated Solid-State Synthesis

摘要

Processing of dense potassium tantalate ceramics is a challenging task. In our study, KTaO_3 powder was prepared by heating the mechanochemically activated K_2CO_3-Ta_2O_5 powder mixture at 800 C for 4 h. Another heating at 800 C was needed to improve the structural homogeneity of the powder. Sintering in air and oxygen atmospheres at 1325℃ for 1 h resulted in the ceramics with relative densities around 85% and inclusions of the K_6Ta_(10.8)O_(30) secondary phase. Phase-pure KTaO_3 ceramics with relative densities of 98% and 95% were obtained by hot-pressing the single- and the double-calcined powder compacts, respectively, at 1250℃ for 2 h. The dielectric permittivity of the hot-pressed ceramic, prepared from the double-calcined powder, measured at 5 K and 1 kHz is 4080, which is almost twice the value obtained for the ceramic, prepared from the single-calcined powder, i.e. 2450, and is comparable with the value reported for the single crystals.