Field-Induced Strain Behavior for Potassium Sodium Bismuth Titanate Ceramics

Data are reported for the dielectric, ferroelectric, piezoelectric and electrostrictive properties of potassium substituted sodium bismuth titanate. For the morphotropic phase boundary composition, relaxor-type behavior was observed at room temperature with ferroelectric (P_R = 25 muC/cm², E_C = 30 kV/cm) and piezoelectric properties (d₃₃ = 325 10^-12 m/V). With increasing temperature a transition to relatively frequency independent diffuse phase transformation occurred, with no remanent strain or coercive field. The field-induced strain was consistent with contributions from electrostriction and field-induced piezoelectricity (M₃₃₃₃ =1.9ldr10^-12 m/V and d₃₃₃ = 81ldr10^-12 m/V at 100degC). Information is given for the temperature dependence of properties, e.g., 0.14% strain induced at 50 kV/cm at 200degC. For certain applications the material compositions are competitive with PZT, especially at higher temperatures.