Defect Dipoles and Internal Bias Field in Glycine Phosphate-Doped Glycine Phosphite Crystals

Abstract

Temperature dependences of pyroelectric, piezoelectric and dielectric responses of glycine phosphite crystals doped with glycine phosphate, in temperature interval 120–320 K, have been investigated. It was established that, unlike the undoped crystals, glycine phosphite crystals grown from the solution containing 25% of glycine phosphate reveal strongly asymmetric hysteresis loops below ferroelectric phase transition temperature T C , and considerable pyroelectric and piezoelectric activity was observed both below and above T C . Analysis of the shape of the hysteresis loops and temperature dependences of dielectric permittivity with and without external biasing points to the existence of internal bias field ∼ 5 kV/cm along the twofold symmetry axis. Possible origin of the internal bias field is discussed.