Influence of Ba2+ doping on the properties and thermal stability of γ-Ce2S3

Abstract

In this study, Ba2+-doped γ-Ce2S3 was successfully prepared via a co-precipitation reaction method using Ce (NO3)3·6H2O, Ba (NO3)3, (NH4)2CO3, and CS2 as raw materials. The effects of different molar ratios of Ba2+ to Ce3+ (nBa/Ce = 0–0.6) on the phase composition, chromaticity, and thermal stability of γ-Ce2S3 were systematically investigated. Pure γ-Ce2S3 was obtained by calcining samples with the Ba2+/Ce3+ molar ratio 0.1–0.5 at 900 °C for 150 min. Under the same conditions, the undoped samples exhibited a pure α phase, while for the Ba2+/Ce3+ ratio of 0.6, a new heterogeneous phase, BaS formed. As nBa/Ce increased, the band gap of γ-Ce2S3 increased from 2.06 to 2.31 eV, which led to the color change from red to orange–red and finally, to yellow. The redness value a* reaches a maximum (L* = 33.51, a* = 37.07, b* = 27.18) when nBa/Ce = 0.1. The samples with nBa/Ce = 0.1 still presented the γ phase and showed excellent chromaticity (L* = 30.10, a* = 25.33, b* = 12.71) after heat treatment at 440 °C for 10 min in air. The results fully show that Ba2+ doping filled the internal vacancies of γ-Ce2S3 solid solution, which was beneficial for the stability of its lattice, thus improving the thermal stability of γ-Ce2S3 (from 350 to 440 °C).