Pressure-Temperature Phase Diagram of KNbO 3 Determined by a Dielectric Constant Measurement

Abstract

The p-T phase diagram of KNbO 3 was studied by measurements of dielectric constant in the temperature region of 150 K to 700 K and in the pressure range up to 10.5 GPa. The stable temperature regions of the orthorhombic and tetragonal intermediate phases became narrower with increasing pressure, but were clearly detected at pressures up to 10.5 GPa. All of the phase transition temperatures from the ferroelectric rhombohedral to orthorhombic, to tetragonal, and then to the paraelectric cubic phase decreased with increasing pressure. At room temperature, the orthorhombic-tetragonal transition takes place at 8.5 GPa, and the tetragonal-cubic transition presumably at about 11 GPa.