Dilatometric and Dielectric Studies of Ferroelectric NaNO₂ in the Vicinity of the Curie Temperature

Abstract

In order to study the phase transitions of ferroelectric NaNO₂ near the Curie temperature T_C and the Néel temperature T_N, the linear thermal expansions x_i(i=a, b, c) and the dielectric constant ϵ_b of the single crystals were simultaneously measured. The formers were measured by means of a clip-type strain gauge dilatometer and the latter was measured on the frequency of 100 kHz by the temperature rate of change of 10 mK/min. The dc biasing field of 4 kV/m was intermittently applied for every other second in order to avoid the influence of ferroelectric domain existence. Each coefficient α_i(i=a, b, c) of the linear thermal expansion showed some anomalies around the T_C and a λ -type anomaly at the T_N. No other evidence of a phase transition was found in the antiferroelectric phase between the T_C and the T_N except around the T_C.

Keywords:

• NaNO₂
• ferroelectricity
• thermal expansion
• strain gauge
• dielectric constant

Acknowledgements

We would like to thank Mr. K. Atobe for his assistance of the measurements.