Emission spectra in Ca1-xCdxS solid solution at 77 and 300 K

Abstract

Solid solutions of Ca1-xCdxS have been prepared for 0.12 <=x<= 0 from mixed sulphates in flowing H2/H2S at 1050°C. Compositions have been determined by atomic absorption spectrophotometry recognising the difficulties in retaining cadmium. A monotonic linear variation of lattice parameter with composition is observed with the rock salt structure being sustained throughout. Both emission and excitation spectra have been determined at 77 and 300 K throughout the composition range. Excitation at wavelengths shorter than the band edge gave rise at 300 K to increased emission in the ultraviolet-violet region between 320 and 420 nm for x between 0.008 and 0.04, whilst at 77 K the emission was restricted to a 390 nm peak with excitation by longer wavelengths at 280 to 285 nm. Cooling to liquid nitrogen temperatures generally sharpened the emission peaks and increased intensities by up to two orders of magnitude. The absorption edge is observed to decrease linearly with increasing cadmium content. An explanation for the excitation and emission behaviour with change in temperature and composition is discussed.