Effect of Hydrostatic Pressure on Ferroelectricity of KNO₃

Abstract

The pressure dependences of spontaneous polarization and dielectric constant of KNO₃ single crystals were measured under hydrostatic pressure up to 3,000 kg/cm². At 130°C, the spontaneous polarization is almost independent of pressure, keeping up the magnitude of 10.4 μC/cm². The dielectric constant in paraelectric phase, phase I, obeys the Curie-Weiss law. The Curie constant C is, however, dependent on pressure. It can be expressed as
C(p)=5.63×10³−0.68×10³p(°K)
with p in 10³ kg/cm². The temperature difference T_c(p)−T₀(p) also depends on the pressure, and can be expressed as
T_c(p)−T₀(p)=89.7−11.2p(°K)
These results are discussed from a phenomenological theoretical point of view.