Rapid Synthesis and Sintering of La2O2S and Its Physical, Optical, and Mechanical Properties

Abstract

Rare-earth oxysulfides are a class of functional ceramic materials with excellent physico-chemical properties and rich functionality. In this study, La2O2S powders were prepared from La2S3 and La2O3 powders at 1000 °C by pressureless sintering. La2O2S compacts were synthesized from La2S3 and La2O3 powders at 800–1600 °C by spark plasma sintering. The influences of sintering temperature and time on the preparation of La2O2S were studied. XRD results indicated that La2O2S ceramics were synthesized successfully and that the lattice constants of La2O2S were close to the theoretical values. SEM showed that the microstructure of La2O2S compacts was homogeneous. The specific heat of La2O2S mainly came from lattice contribution, and its Debye temperature was 237 K. The UV–visible absorption spectra showed different absorption levels in the 240–300 nm range. Raman spectroscopy revealed distinct peaks at different temperatures, indicating changes in the covalence band. The relative density of La2O2S ceramics was 92% and lower than theoretical values. Hardness of the synthesized La2O2S was greater than that of Gd2O2S ceramics.