FORMATION AND OPTICAL-PROPERTIES OF HOMOGENEOUS SOLID-SOLUTIONS OF CA1-XSRXS-CE

Samples of Ca1-xSrxS:0.001 Ce were prepared by reduction of mixed sulphates with H-2/H2S at elevated temperatures. In the absence of a flux, only at 1200-degrees-C for long reaction times did near complete solid solution occur. However, addition of LiF flux to samples prepared at 1100-degrees-C did yield homogeneous single phase mixed sulphides but of poor crystallinity. Photoluminescence excitation and emission spectra were determined for these solid solutions at 295 and 77 K. Peak emission wavelengths at 77 K ranged from 500 nm for CaS: Ce to 478 nm for SrS : Ce. The wavelength shift reflects the sensitivity of the 5d state of the Ce3+ ion to the strength of the crystal field.