Phase equilibria and processing of infrared optical ceramics on the join CaLa₂S₄-La₂S₃

Processing techniques have been developed for the fabrication of optically transparent, theoretically dense CaLa2S4-La2S3 ceramics with a potential application as windows for the mid-infrared. Extreme care is needed to avoid oxygen. Best results were obtained by pre-sintering in an H2S/H2 atmosphere followed by hot-isostatic pressing. Microstructures, hardness measurements, and infrared absorption spectra serve to characterize the various processing procedures.