Formation and densification of CaLa 2S 4 powders by sulfidization of modified metal alkoxides in different atmospheres

Abstract

Highly sinterable submicron CaLa 2S 4 (CLS) powders with high La/Ca ratios were prepared by sulfidizing calcium and lanthanum alkoxides under CS 2 gas for 8 h and then in a pure H 2S atmosphere for 8 h at 550–950°C. It is for application in infrared transmitting window of 8–14 μm wavelength. In the range of La/Ca ratios from 10 to 15, the phases obtained are LaS 2 intermediate phase at low temperature (550°C), a β-La 2S 3 minor phase at 650°C, and a pure Th 3 P 4 phase after 850°C treatment. After HIP’ing and annealing in an H 2S atmosphere at 1350°C, the Pb 0.1Ca 0.9La 2S 4 pellet without extrinsic absorption in the 2.5–7 μm range due to carbon contamination was obtained by sulfidizing at 850°C for 8 h in CS 2 gas and then at 850°C for 8 h in H 2S atmosphere. The characteristic absorption bands of sulfate and sulfite at 9.2 and 11 μm were reduced by eliminating the oxygen residue in the sulfide by using the powder sulfidized at 750°C in CS 2 gas and then at 850°C for 8 h in H 2S atmosphere.