Аннотация:The fabrication of high-quality crystal layers has been an active research topic in the field of modern materials chemistry with potential applications in various industrial fields. In particular, photocatalytic water splitting, in which hydrogen and oxygen molecules are directly dissociated from water using solar energy and visible-light-driven photocatalysts, is a potentially economical and green process for producing clean and renewable hydrogen energy. In this work, films of three crystalline oxides, Ba5Ta4O15, Sr5Ta4O15, and Sr2Ta2O7, and one crystalline oxynitride, BaTaO2N, were grown using the flux-coating technique in molten chloride salts (flux) at 1000 °C. The film growth was studied under several different conditions. In particular, we investigated the effect of three different atmospheres (air, nitrogen, and ammonia) on the growth behavior and composition of the polycrystalline layers grown from a BaCl2·2H2O flux. We found that the growth atmospheres were important in forming idiomorphic crystals with well-developed facets and characteristic shapes. In particular, idiomorphic Ba5Ta4O15 crystals shaped like elongated hexagons were grown vertically and densely packed on the TaOx/Ta metal surface. Ba5Ta4O15 is thought to be formed by a reaction between the Ba source and TaOx in the flux. Furthermore, under an NH3 gas atmosphere, densely packed BaTaO2N crystals were directly grown on the Ta metal surface. We achieved the growth of relatively thick crystal layers using our flux-coating method.
