Peculiarities in thermal linear expansion and refractive indices of (NH2CH2COOH)center dot H3PO3 single crystals in the region of phase transition

Temperature dependences of thermal linear expansion and optical path differ ence determined by the refractive index (200 to 270 K) and spectral depende nces of refractive indices and optical birefringence (475 to 700 nm) of gly cine phosphite [GPI: (NH2CH2COOH).H3PO3] Single crystal have been measured. The characteristic indices 2 beta of power-like temperature dependence for the parameters measured have been determined to be temperature dependent, The coefficients of electrostriction and quadratic electrooptic effect of G PI crystal decrease at approaching the phase transition temperature T-c whe n going from the ferroelectric phase.