氧-水蒸汽中Sr_2GdRuO_6纯相的合成及固相反应机理

Preparation of Sr_2GdRuO_6 in Oxygen-water Vapor Mixed Atmosphere and Its Mechanism of Solid State Reaction*

采用氧 (或空气 ) 水蒸汽混合气氛下的固相反应 ,可合成无任何SrRuO3 杂相的纯相化合物Sr2 GdRuO6.当由Sr2 GdRuO6作先驱物 ,类似的固相反应体系 ,可成功合成无任何SrRuO3 杂相的纯相RuSr2 GdCu2 O8化合物 .此外 ,还讨论了有水蒸汽参与的固相反应合成Sr2 GdRuO6的反应机理 .结果表明 ,水蒸气的作用是抑制SrRuO3 的形成 ,而不是有利于把SrRuO3 杂相转化为Sr2 GdRuO6相 .

Sr2GdRuO6 which is always used as a precursor in synthesizing superconducting cuprate RuSr2GdCu2O8, prepared by common solid state reaction in air or in O-2 is always accompanied by the formation of small amounts of ferromagnetic SrRuO3 impurities phase. It is reported in this paper that the pure phase compound Sr2GdRuO6 without any ferromagnetic SrRuO3 impurity phase is successfully prepared via solid state reaction in O-2 ( or air)-water vapor mixed atmosphere. The pure phase compound RuSr2GdCu2O8 without any ferromagnetic SrRuO3 impurities phase is also obtained via analogous solid state reaction system using the pure phase compound Sr2GdRuO6 as a precursor. In addition, the mechanism of the solid state reaction in the presence of water vapor is also discussed. It suggests that the vapor is not beneficial to transformation of SrRuO3 to Sr-2 GdRuO6, and the effect of water vapor on the solid state reaction is to suppress the formation of SrRuO3 due to the formation of RuO2 (.) nH(2)O in the water vapor atmosphere.