Microstructure and electrical properties of tungsten-doped bismuth titanate ceramics

Bismuth-layer-structured Bi4Ti3-xWxO12+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 10(8) Omegacm at 400degreesC 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 Bi4Ti2.96W0.04O12.04, which possessed a high electrical resistivity and a good temperature stability of dielectric properties than other composition materials.