Study of K+ doping on structure and properties of γ-Ce2S3

Abstract

In this study, K+-doped γ-Ce2S3 was successfully prepared via a gas–solid reaction method using CeO2, K2CO3, and CS2 as raw materials. The effects of the suitable sulfide system and different molar ratios of K to Ce (nK/Ce = 0–0.30) on the phase composition, crystal structure, chromaticity and thermal stability of γ-Ce2S3 were systematically investigated. Pure γ-Ce2S3 was obtained by calcining the doped samples at 840 °C for 150 min. After calcination at the same temperature the undoped K+ samples exhibit a pure α-phase. Samples with a K/Ce molar ratio (nK/Ce) of 0.10–0.25 comprise only the γ-phase; and when nK/Ce exceeds 0.25, a new heterogeneous phase, KCeS2, emerges. For values of nK/Ce in the range of 0–0.25, the γ-Ce2S3 lattice parameters gradually increases with increasing K+ content. When nK/Ce exceedes 0.25, the lattice parameters remains unchanged. As nK/Ce increased, the synthesized color gradually changes from red to orange–red and finally, to yellow. The redness value a* reaches the maximum (L* = 33.86, a* = 36.68, b* = 38.15) when nK/Ce = 0.10. The nK/Ce = 0.10 composition continues to exhibit the γ-phase after heat treatment at 420 °C for 10 min in air. The K+ doping fills the internal vacancies of γ-Ce2S3 and formed a solid solution, which is beneficial for the stability of its lattice, thus improving the thermal stability of γ-Ce2S3 (from 350 to 420 °C).