Crystal growth study of CaGa 2S 4 Co-doped with Ce 3+ and Na +

Abstract

We have examined the effects of co-doping of Ce 3+ and Na + in CaGa 2S 4. Differential thermal analysis and X-ray diffraction analysis were carried out on the compounds of Ca (1− x )Ce x /2Na x /2Ga 2S 4 (0⩽ x⩽1) to obtain the necessary information for their synthesis. It is shown that Ce 3+ and Na + can be simultaneously doped into CaGa 2S 4 up to about 30 mol% ( x=0.6). The melting point was determined as a function of x. Photoluminescence (PL) was measured with these products, where the maximum intensity was found at 10 mol% ( x=0.2). Single crystals of Ca (1− x )Ce x /2Na x /2Ga 2S 4 ( x=0.02 and 0.2) were grown from melt by the horizontal Bridgman method. Light absorption was measured near the fundamental absorption edge using a high quality part of the single crystals. Photoluminescence excitation (PLE) spectra were also measured using compounds of Ca (1− x )Ce x /2Na x /2Ga 2S 4 with x=0.02, 0.2 and 0.5 and a Ce only-doped CaGa 2S 4:Ce + (0.8 mol%).