Preparation of R2S3 (R: La, Pr, Nd, Sm) powders by sulfurization of oxide powders using CS2 gas

In the synthesis of La2S3 via the sulfurization of La2O3 powder using CS2 gas, La2O2S was formed in the initial stage of reaction, and single-phase β-La2S3 were finally formed for a shorter period of time at higher temperature. For long sulfurization time of 8 h, single-phase β-La2S3 could be synthesized at above 1023 K. In the synthesis of Pr2S3 via the sulfurization of Pr6O11 powder using CS2 gas, PrS1.7, Pr4O7, and Pr2O2S were formed as intermediate products. At sulfurization temperatures above 1123 K, only Pr2O2S was formed in the initial stage of reaction, and α-Pr2S3 having a trace of β-Pr2S3 was formed for a shorter period of time at higher temperature instead of Pr2O2S. In the synthesis of Nd2S3 and Sm2S3 via the sulfurization of Nd2O3 and Sm2O3 powders using CS2 gas, only Nd2O2S and Sm2O2S were also formed in the initial stage of reaction. And α-Nd2S3 having a trace of β-Nd2S3 and single phase α-Sm2S3 were formed for a shorter period of time at above 1073 and 1123 K, respectively. In all cases, the impurity oxygen content in synthetic powders decreased gradually with an increase in sulfurization temperature. Moreover, the carbon content in these powders increased gradually with an increase in the sulfurization temperature.