Delafossite CuYO_2 and Ca doped CuYO_2 were prepared by thermal decomposition of a metal-citric acid complex. The starting solution consisted of Cu acetate, Y acetate and Ca acetate as the raw materials. Citric acid was used as the chelating agent, and acetic acid and distilled water were mixed as a solvent. The starting solutions were heated at 723K for 5h after drying at 353K. The obtained powders were amorphous and single phase of orthorhombic Cu_2Y_2O_5 was obtained by heat-treated the amorphous powder at a temperature range between 1073 and 1373K for 3h in air. Furthermore, Heat-treating the obtained orthorhombic Cu_2Y_2O_5 at above 1373K in air caused it to decompose into Y_2O_3, CuO and Cu_(2O). On the other hand, the sample powder prepared from a starting solution without citric acid, i.e., single phase of orthorhombic Cu_2Y_2O_5 could not be obtained under the same synthesis conditions as that for a solution with citric acid. We were able to obtain delafossite CuYO_2 and Ca doped CuYO_2 from orthorhombic Cu_2Y_2O_5 under a low O_2 pressure atmosphere at above 1223K. The obtained delafossite CuYO_2 composed hexagonal and rhombohedral phases. The color of the CuYO_2 powder was light brown and that of Ca-doped CuYO_2 was light green. Diffraction peaks in the XRD pattern were slightly shifted by doping Ca for CuYO_2, and these peaks shifted toward to a high diffraction angle with an increasing amount of doped Ca, From these results, we concluded that Ca doped delafossite CuYO_2 could be obtained by thermal decomposition of a metal-citric acid complex.
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