Phase-relations study of Sr-Mo-O system for new superconductors search

In order to obtain single-phase samples of perovskite-related strontium molybdates, especially of Sr2MoO4, we started to explore the ternary phase diagram of Sr-Mo-O. When we heated in an evacuated quartz tube the starting material whose composition was Sr : Mo: O = 2 : 1 : 4, we obtained no Sr2MoO4 phase. By using the compositions away from 2: 1 :4, we found multi-phase samples containing Sr2MoO4, Sr3Mo2O7, and Mo metal. However, we were able to obtain single-phase samples of Sr2MoO4 from the stoichiometrically-prescribed starting materials by proper control of atmosphere in the quartz tube. We emphasize that for new superconductors search in metal oxides we should avoid the use of SrO as a starting material in order to suppress the formation of metal carbides.