Spontaneous birefringence of flux grown single crystals of the ferroelectric/antiferromagnetic perovskite lead iron tantalate (PbFe1/2Ta1/2O3) (PFT)

The spontaneous birefringence Δns of the rhombohedral ferroelectric phase of PFT has been measured between 20 K and the hitherto unknown first order transition at 210 K (heating)/205 K (cooling). Above that transition there is a weakly birefringent phase, which undergoes a second order transition to cubic at ∼248 K. Pronounced photoconductivity occurs below room temperature. A strong reversible temperature shift (-5.7 cm-1 K-1) of the absorption edge obscures the material upon heating