Electric-field-dependent phase volume fractions and enhanced piezoelectricity near the polymorphic phase boundary of (K0.5Na0.5)(1-x)LixNbO3 textured ceramics

The structure, ferroelectric and piezoelectric properties of < 001 > textured (K0.5Na0.5)(0.98)Li0.02NbO3 ceramics were investigated as a function of temperature and dc bias E. X-ray diffraction revealed an orthorhombic (O) -> tetragonal (T) polymorphic phase boundary (PPB). Phase coexistence was found near the PPB over a 30 degrees C temperature range, where the relative phase volume fractions changed with temperature. Furthermore, increasing E applied along the < 001 > texture direction resulted in a notable increase in the volume fraction of the T phase at the expense of the O phase, effectively shifting the O -> T boundary to lower temperature. An enhancement in the piezoelectric properties was found to accompany this increase in the T volume fraction.