Electric-field-dependent phase volume fractions and enhanced piezoelectricity near the polymorphic phase boundary of (K0.5Na0.5)1−xLixNbO3textured ceramics

Abstract

The structure, ferroelectric and piezoelectric properties of $\ensuremath{\langle}001\ensuremath{\rangle}$ textured (K${}_{0.5}$Na${}_{0.5}$)${}_{0.98}$Li${}_{0.02}$NbO${}_{3}$ ceramics were investigated as a function of temperature and dc bias $E$. X-ray diffraction revealed an orthorhombic ($O$) \ensuremath{\rightarrow} tetragonal ($T$) polymorphic phase boundary (PPB). Phase coexistence was found near the PPB over a 30 \ifmmode^\circ\else\textdegree\fi{}C temperature range, where the relative phase volume fractions changed with temperature. Furthermore, increasing $E$ applied along the $\ensuremath{\langle}001\ensuremath{\rangle}$ 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 $O$ \ensuremath{\rightarrow} $T$ boundary to lower temperature. An enhancement in the piezoelectric properties was found to accompany this increase in the $T$ volume fraction.