Optical and dielectric studies on ferroelectric oxyfluoride k3moo3f3 single crystals

Ferroelectric oxy fluoride K3MoO3F3 single crystals prepared by the Bridgman method have been studied by means of polarized light microscopy and dielectric measurements. Analysis of the ferroelastic domains indicated a first order phase transition at TC=528 K from a ferroic phase to a cubic (m3m) one. Domain structures are consistent with a trigonal symmetry below TC. Continuous measurements of the temperature dependence of birefringence and dielectric permittivity between 300 and 600 K led to the disclosure of an additional phase transition of 1st-order at TC=453 K.