SYNTHESIS OF A SPINEL-TYPE FERROMAGNETIC SEMICONDUCTOR, CDCR2SE4 AND MEASUREMENTS OF OPTICAL-SPECTRA

Synthesis of CdCr2Se4 spinel for optical spectra measurements has been carried out by the dry technique at 773, 873 and 973 K. Although near ly single phase was obtained at 873 and 973 K after extremely long per iod of heating, say 47 d, of presintered materials at 773 K, 100 d hea ting at 773 K did not yield single phase due to firm association of ac cessory phases of CdSe and Cr2Se3. EPMA mapping analysis for such samp les showed the independent presence of massive grains of CdSe among th e spinel grains and disseminated presence of Cr2Se3 in the spinel grai ns as inclusions, This isolate presence of CdSe and Cr2Se3 is probably the main cause of preventing the formation of the spinel single phase in a short period of time. Unit-cell parameters, spinel u-parameters and band gaps as measured by XRD and optical spectroscopy were 1.0744- 1.0749 nm. 0.388-0.389 and 1.27-1.30 eV, respectively, depending on sy nthetic conditions.