Minor Dielectric Anomalies in AnbO_3 (A-Li, Na, K) Single Crystals in the 100-300 deg C Temperature Range

摘要

In AnbO_3 (A-Li, Na, K) single crystals besides dielectric permittivity e maxima, corresponding to the known ferroelectric and antiferroelectric phase transitions, minor epsilon(T) anomalies were observed in the 100-300 deg C temperature range. The temperature T_a of these anomalies does not depend on measuring frequency in the 10~2-10~6 Hz range. Dilatotnetric studies showed that temperature dependences of relative dilatation AZ/L have an inflexion in the vicinity of T_a. Linear correlation between Ta and the temperature TPE of the phase transition into the paraelectric phase was revealed. It is supposed that the minor epsilon(T) anomalies observed in AnbO_3 crystals in the 100-300 deg C temperature range are due to phase transitions to the incommensurate phase.