Dielectric and Thermal Study of K_2SeO_4 Transitions

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The behaviours of the various dielectric properties and specific heat of potassium selenate, K_2SeO_4, have been studied with particular reference to the transitions at 129.5°K and 93°K the crystal is ferroelectric along the c axis. The spontaneous polarization and coercive field determined from the hysteresis loop are 6.5×10^<-8>coul/cm^2 and 60V/cm respectively at 80°K. The curve of dielectric constant vs temperature obeys the Curie-Weiss law about the Curie point and the Curie constants for warming and cooling processes are 27°K and 130°K respectively. The Curie temperature varies almost linearly with the biasing field with the coefficient of 0.19°/KV/cm. Effects of the γ-radiation on the dielectric behaviour are observed. Discontinuity of the specific heat of about 2.3cal/mol・deg has found at the transition of 129.5°K. Anomaly at the transition of 93°K is very small. The transition energy and the entropy change are estimated to be of the order of 0.5cal/mol and 5×10^<-3>cal/mol・deg of less respectively. The higher temperature transition is of second order and the lower of first order.
社団法人日本物理学会の論文
1970-02-05