Electromechanical Behavior of Single Crystals of Barium Titanate from 25 to 160°C

Abstract

Dynamic piezoelectric resonance measurements have been made on single crystals of barium titanate in the temperature range from room temperature to 160°C. In the ferroelectric region (room temperature to 120°C) the material is spontaneously polarized and hence naturally piezoelectric. For this range of temperature results are presented for the elastic compliance coefficients s₁₁^E and s₁₁^P, the combination (2s₁₂+s₆₆) at constant field and constant polarization, and the piezoelectric coefficient d₃₁ as functions of temperature. Above the Curie temperature (120°C) the piezoelectric resonances can be observed only by polarizing the crystal with an external field. From measurements of the resonant frequencies in crystals having their longitudinal axes along the (100) and the (110) direction, and the assumption of the validity of the Cauchy relation (c₁₂=c₄₄), the elastic coefficients at constant polarization have been determined as functions of temperature and polarization from the Curie point to 160°C. The strains induced by the polarization in a stress‐free crystal are shown to be proportional to the square of the polarization, for values of polarization up to one‐third of the spontaneous polarization at room temperature.