Piezoelectric properties in the perovskite BiScO3-PbTiO3-(Ba,Sr)TiO3 ternary system

A new ternary system (1 - x)BiScO3-x{(l - y)PbTiO3-y(Ba0.294Sr0.706)TiO3}was studied in relation to morphotropic phase boundaries (MPB). Analogous to modified PZT ceramics, barium and strontium were introduced to the recently developed MPB (1 - x)BiScO3-xPbTiO(3) for x > 0.60, in order to investigate Curie temperature and piezoelectric property variations. With increasing barium and strontium substitution up to y = 0.3, the MPB line moved from x = 0.64 to 0.70 and d(33) and k(p) gradually decreased. X-ray diffraction phase analysis correlated the variations in piezoelectric properties showing a maximum in the compositions near rhombohedral-tetragonal phase boundary. Grain sizes were around 2 mum for all compositions and tetragonality decreased with the downward shifting of T-c in the range of 216-371degreesC. The frequency dependence of dielectric properties about the Curie maximum shows a dispersion in both epsilon' and tan delta. This relaxation behavior becomes more pronounced with increasing (Ba,Sr)TiO3 content, and high Curie maximum temperatures T-max's are found compared to lead based perovskites with complex B-sites.