Mechanically induced change of birefringence in LiKSO4 crystals

The effects of uniaxial mechanical stresses sigma(z) and sigma(y) on the temperature (77-300 K) and spectral (250-850 nm) changes of the birefringence were studied LiKSO4 crystals. A dissimilarity in the behavior of birefringence Delta n(i) is revealed, namely, under sigma(y), the value of Delta n(i) linearly decreases, whereas under sigma(z) it increases linearly in the whole spectral range. A substantial shift of the phase transition points under sigma(y) and sigma(z) is found as well as an enhancement of the thermal hysteresis of the transition from incommensurate to commensurate ferroelastic phase. It is shown that under pressure the temperature-spectral diagram of the isotropic state of the crystal is substantially modified.