Formation and densification of CaLa2S4 powders by sulfidization of modified metal alkoxides in different atmospheres

Highly sinterable submicron CaLa2S4 (CLS) powders with high La/Ca ratios we re prepared by sulfidizing calcium and lanthanum alkoxides under CS2 gas fo r 8 h and then in a pure H2S atmosphere for 8 h at 550-950 degrees C. It is for application in infrared transmitting window of 8-14 mu m wavelength. I n the range of La/Ca ratios from 10 to 15, the phases obtained are LaS2 int ermediate phase at low temperature (550 degrees C), a beta-La2S3 minor phas e at 650 degrees C, and a pure Th3P4 phase after 850 degrees C treatment. A fter HIP'ing and annealing in an H2S atmosphere at 1350 degrees C, the Pb0. 1Ca0.9La2S4 pellet without extrinsic absorption in the 2.5-7 mu m range due to carbon contamination was obtained by sulfidizing at 850 degrees C for 8 h in CS2 gas and then at 850 degrees C for 8 h in H2S atmosphere. The char acteristic absorption bands of sulfate and sulfite at 9.2 and 11 mu m were reduced by eliminating the oxygen residue in the sulfide by using the powde r sulfidized at 750 degrees C in CS2 gas and then at 850 degrees C for 8 h in H2S atmosphere. (C) 2000 Elsevier Science S.A. All rights reserved.