Hydrothermal synthesis of Ba5Nb4O15 ultrafine powders

Ba5Nb4O15 ultrafine powders were prepared by hydrothermal method using Ba(NO3)2 and Nb2O5 precursors. The synthesis characteristics were influenced by the chemical form of precursors, reaction temperature, mole ratio of Ba/Nb and pH value. The chemical form of the precursors has a strong influence on the products of Ba5Nb4O15. There was no requisite compound in the final product when Nb2O5 powder was used as Nb-precursor. In addition, the reaction completeness was also dependent on the synthesis temperature. The best single phase Ba5Nb4O15 ultrafine powders were obtained at a temperature of 230 °C. The most appreciate Ba/Nb molar ratio was 3/2. The reactions were only carried out in a solution with pH value between 12 and 14. When pH was equal or larger than 14, there was no product of Ba5Nb4O15 powder in the reactor.