传统固相反应所合成的锶系钌铜氧化物,通常总伴有少量铁磁性SrRuO3杂相.采用氧(或空气)-水蒸气混合气氛下的新型固相反应,既能成功合成锶系钌铜氧化物的前驱物纯相Sr2GdRuO6(211相), 也能进一步在相对低的温度下成功合成锶系钌铜氧1222纯相化合物RuSr2(Gd,Ce)2Cu2O10 (Ru-1222),使其中SrRuO3杂相含量大大减少.详细讨论了新型固相反应下产物的形成及其机理,并涉及SrRuO3杂相的存在对RuSr2(Gd,Ce)2Cu2O10产物电学性质的影响.结果表明,水蒸气的作用能抑制前驱物合成中SrRuO3杂相的形成,进而控制反应产物Ru-1222相中SrRuO3杂相的存在,而后者又有利于Ru-1222相超导电性的获得.
Sr-Ru cuprates synthesized via traditional solid-state reaction is always accompanied by the formation of small amounts of SrRuO3 impurity phase with ferromagnetism. In this paper we report that not only the pure phase compound Sr2GdRuO6 without any ferromagnetic SrRuO3 impurity phase is successfully prepared by means of a new-type reaction of solid state in presence of O-2 (or air)-water vapor mixed atmosphere, but also RuSr2 (Gd, Ce)(2)Cu2O10 (Ru-1222) without any ferromagnetic SrRuO3 impurity phase is further synthesized under a relative low reactive temperature when the Sr2GdRuO6 is used as a precursor. The authors discuss the formation of the product Sr2GdRuO6 and mechanism of the new-type reaction of solid state in presence of water vapor in detail. In addition, the effects of SrRuO3 impurity phase on the electric properties of the product Ru Sr-2(Gd,Ce)(2)Cu2O10 is also discussed. It suggests that the water vapor for the new-type solid-state reaction is not beneficial to the transformation of SrRuO3 uO(3) to Sr2GdRuO6, and it is to suppress the formation of SrRuO3 due to the formation of RuO2 - nH(2)O. Thus the amount of SrRuO3 impurity phase in Ru-1222 phase is controlled in the reaction of solid state. It seems that the presence of a small amount of SrRuO3 impurity phase is favourable for making the Ru-1222 phase superconductive.
Acta Physica Sinica