Microstructure and Electrical Properties of Tungsten-Doped Bismuth Titanate Ceramics

Bismuth-layer-structured Bi₄Ti_3-xW_xO_12+x (BiTW) ceramics, where x=0, 0.02, 0.04, 0.08, 0.10 and 0.20, have been prepared by a conventional sintering technique. The conducting, dielectric and ferroelectric properties of BiTW were investigated. The microstructure results revealed randomly oriented grains with a needle structure, and the grain size decreased gradually with increasing W⁶⁺ doping content. The conducting properties were studied in a direct-current circuit at various temperatures. W⁶⁺ donor doping enhanced the electrical resistivity markedly above 10⁸ Ωcm at 400°C on the whole. BiTW with suitable W⁶⁺ replacement showed good temperature stability from the temperature dependence of dielectric constant. T_c decreased gradually with W doping. Ferroelectric hysteresis loops were also determined for various x values. Excellent properties could be found at x=0.04, i.e., the composition Bi₄Ti_2.96W_0.04O_12.04, which possessed a high electrical resistivity and a good temperature stability of dielectric properties than other composition materials.