Investigation of high Curie temperature (1-x)BiSc1-yFeyO3-xPbTiO3 piezoelectric ceramics

Ceramics around the morphotropic phase boundary (MPB) in the (1-x)BiSc1-yFeyO3-xPbTiO3 solid solution were fabricated. For y=0.5, ceramics were single phase, and piezoelectric coefficients (d(33)) and electromechanical coupling coefficients (k(p)) for MPB compositions were 300 pC/N and 0.49, respectively; a level of piezoelectric activity similar to that of hard, lead zirconate titanate compositions but with T-C similar to 60 degrees C higher at similar to 440 degrees C. For ceramics with y >= 0.7, dielectric measurements in combination with diffraction contrast transmission electron microscopy revealed the existence of two ferroelectric phases for most PbTiO3 contents studied. The presence of two ferroelectric phases was associated with a decrease in piezoelectric activity and although raw materials costs for y=0.7 and 0.8 with respect to y=0 were significantly lower (less Sc2O3) and T-C greater (similar to 500 degrees C), d(33) (similar to 100 pC/N) and k(p) (0.18) were too low to be commercially useful for actuator applications. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3253585]