METHOD FOR PRODUCING HALIDE

The production method of the present disclosure includes heat-treating a material mixture containing a compound containing Y, a compound containing Sm, NHα, Liβ, and Caγin an inert gas atmosphere. The compound containing Y is at least one selected from the group consisting of YOand Yδ, and the compound containing Sm is at least one selected from the group consisting of SmOand Smε. The material mixture contains at least one selected from the group consisting of YOand SmO, and α, β, γ, δ, and ε are each independently at least one selected from the group consisting of F, Cl, Br, and I.