Dielectric and piezoelectric properties of BiScO3-PbTiO3 crystals with morphotropic phase boundary composition

The room temperature dielectric permittivity of [100] oriented 0.37BiScO(3)-0.63PbTiO(3) (BSPT63) crystals with a morphotropic phase boundary (MPB) composition was found to be 1400, lower than that of BSPT57 crystals with rhombohedral phase (similar to3000), but much higher than that of the tetragonal crystal BSPT66 (similar to200). The Curie temperature of BSPT63 single crystals along [100] was found to be about 443degreesC, while the values were around 440degreesC and 445degreesC for [110] and [111] oriented crystals, respectively. Evidence of a ferroelectric-ferroelectric phase transformation temperature was associated with a dielectric anomaly occurring around 310-350degreesC for different orientations, indicating a strong curvature of the MPB. The coercive fields (E,) were found to be 20kV/cm for [100] oriented crystals, 24kV/cm and 27kV/cm for [110] and [111] directions, respectively. The piezoelectric response for [100] oriented samples (d(33) = 900pC/N) is weaker than that in rhombohedral phase (d(33) = 1200pC/N) but much higher than that in tetragonal phase (d(33) = 200pC/N). The strain piezoelectric d(33) improved with the temperature increasing owing to dielectric permittivity increment, while the voltage piezoelectric g(33) is independent of temperature (g(33) similar to 0.074m(2)/C). Evidence of a monoclinic phase for BSPT63 crystals is inferred using the X-ray powder diffraction (XRD), and the lattice parameters were calculated to be a = 4.0751 Angstrom, b = 3.9765 Angstrom, c = 3.9893 Angstrom and beta = 90.166degrees.