ABSTRACT Data are reported for the dielectric, piezoelectric, electrostrictive, and ferroelectric properties of potassium-substituted sodium bismuth titanate, [(KxNa1-x)0.5Bi0.5]TiO3. For the morphotropic phase boundary composition x = 0.2, relaxor-type behavior was observed at room temperature with piezoelectric (effective d333 = 325· 10-12 m/V) and ferroelectric properties (PR = 25 μC/cm2, EC = 30 kV/cm). A transition to a relatively frequency-independent, diffuse phase transformation region occurred with increasing temperature, with no remanent strain or coercive field. Above the transition temperature, the field-induced strain was consistent with contributions from electrostriction and field-induced piezoelectricity (M3333 = 1.9· 10-16 m2/V2 and d333 = 81· 10-12 m/V at 100°C). Information is given for the temperature dependence of properties, e.g., 0.14% strain induced at 50 kV/cm at 200°C. Higher potassium content x = 0.6 stabilized the ferroelectric piezoelectric region to temperatures above 200°C, with a relatively stable d333 = 150--145· 10-12 m/V between 25°C and 200°C. Pb-free KNBT ceramics appear competitive with PZT, especially for higher temperature electromechanical applications.
Digital Object Identifier 10.1109/TUFFC.2007.570
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