Anomalous changes of the physical properties of LiKSO₄ crystals in the temperature region from 100 TO 300 K

Abstract

The pyroelectric, dielectric, piezoelectric and elastic properties of LiKSO₄ crystals grown from aqueous solutions at 315 K were studied in the temperature range from 100 up to 300 K. The properties studied were found to exhibit anomalous temperature-dependent variations. It was found that LiKSO₄ crystal undergo a structural phase transition at a temperature of about 190 K. In the vicinity of phase transition temperature changes in sign of the pyroelectric coeffiecient, σP, measured at constant stress σ, and also a relatively small anomalous changes of the dielectric properties of LiKSO₄ crystals were observed. When the crystal was heated from 100 up to 300 K a marked anomalous decrease of the piezoelectric moduli dij and an increase of the elastic stiffnesses cij were also observedl. Furthermore both time and temperature changes of the physical properties of LiKSO₄ crystal point out to the existence of a ferroelastic phase below 190 K. In this way the LiKSO₄ crystal seems to behave different from other known ferroelastic crystals.