Dielectric Properties of Rubidium Nitrate under Hydrostatic Pressure

The relative permittivity ( ε r ) and dielectric conductivity (σ) of RbNO 3 single crystals were measured at 1 MHz under hydrostatic pressures over its two phase transformations; II-III (219°C at l aim) and III-IV (164°C at 1 atm). The value of ε r has a large peak at the II-III phase transition pressure, and 1/ ε r obeys the Curie-Weiss law on pressure in the phase III. This behavior of ε r is elucidated by the phenomenological theory for the first order antiferroelectric phase transition. The II-III phase boundary was determined by the dielectric measurement. At the IV-III phase transition temperature ( T c ), the changes in ε r and σ seen in the ε r vs. T and σ vs. T curves get smaller with increasing applied-pressure. The behavior of ε r and σ is explained by taking account of the rotation of NO 3 - ions being hindered by the pressure.