Phase states and dielectric properties of sodium-potassium niobate solid solutions

The temperature dependence of dielectric constant ɛ for single crystals of Na 1− x K x NbO 3 (0.04≲ x ≲0.15) is studied for the first time. From the shape of the ɛ( T ) anomalies corresponding to rotational phase transitions, the type of interaction between the order parameters and the polarization is determined. A phenomenological model is developed which adequately describes the experimentally observed sequence of high-temperature ( T >300°C) phase transitions, the dielectric anomalies associated with these transitions, and the changes in the phase states under the action of external factors (pressure, electric field).