OPTICAL-PROPERTIES OF PYROCHLORE LEAD SCANDIUM TANTALATE CRYSTALS

Optically homogeneous Pb2Sc0.5Ta1.5O6.5 crystals with pyrochlore struc ture are prepared by the method of high-temperature solution growth (H TSG). The refractive index in the visible region of the spectrum is me asured. From the transmission spectra in the visible and infrared regi on the optical transmission window is estimated. From the fundamental absorption edge in the visible region of the spectrum the optical band gap is determined corresponding to the intrinsic absorption. From the behaviour of the absorption coefficient alpha(hv) and alpha(1/2)(hv) a nd the Raman spectrum permit to suggest that the absorption edge below 2.75 eV is due to indirect transitions.