Stabilization of lanthanum sulfides with different dopants

By introducing different dopants into the lattice, lanthanum sulfides with higher stability were prepared via the sulfurization of lanthanum oxides using CS₂ gas at 1 000 °C. The sulfurizing time of 8 hours was optimized for La/Ca=2 at 1 000 °C and its sulfurization mechanism to form CaLa₂S₄ was via the reaction of β-La₂S₃ with CaS. As the increase of the La/Ca and La/Na ratio, longer sulfurizing time was required to get cubic phase. The investigation indicates that Na⁺ ions were more effective to stabilize cubic structure comparing with Ca²⁺ ions.