Optical and electric investigations of the phase transitions in pyrochlore Cd₂Nb₂O₇

Abstract

Ferroelastic / ferroelectric phase transitions in Cd₂Nb₂O₇ crystals have been analyzed by means of polarized light microscopy associated with electric characterization. The symmetry of the ferroelectric phase below T₂ = 194 K is found to be orthorhombic mm2(pp) with the spontaneous polarization P_S parallel to [001]_cub. By application of an electric field // <100>_cub the mm2(pp) phase remains stable in the whole temperature range of the ferroic phases below T₁ = 204 K, whereas a field // <110>_cub can induce a mm2(ss) phase below T₁.