The hydrostatic pressure dependence of the phase transitions and dielectric properties for a potassium niobate crystal

Abstract The phase transitions, spontaneous polarizations, and dielectric properties of a potassium niobate (KNbO 3 ) ferroelectric crystal were investigated under hydrostatic pressure from 0 to 21.3 GPa using the Landau–Ginsburg–Devonshire phenomenological theory. It was shown that the phase transition temperatures of cubic to tetragonal, tetragonal to orthorhombic, and orthorhombic to rhombohedric decreased as the hydrostatic pressure was increased and the derivative of the phase transition temperatures with respect to hydrostatic pressure could be estimated to be −33.1 °C/GPa. The spontaneous polarizations decreased nonlinearly with increasing hydrostatic pressure which could be attributed to the hydrostatic pressure-induced decrease of the interionic distance. The dielectric susceptibility e 33 increased by about 85% and the dielectric susceptibility e 11 decreased by about 50% when hydrostatic pressure increased from 0 to 4 GPa at 260 °C. It provides a new effective way to improve the pressure sensitivity in acoustic transducer and the energy storage performance of capacitor. The changes of dielectric susceptibilities induced by hydrostatic pressure had been explained by the flattening or steepness of Gibbs free energy profile. As the properties of the ceramics are related to those of the single crystal, results in this paper can be used to explore the general rule of performance change induced by pressure for lead free KNbO 3 -based ceramics.