Synthesis of needlelike leucite crystals using potassium sulfate flux

When a powder mixture consisting of Al-2(SO4)(3), SiO2 and K2SO4 was heated in a closed alumina crucible, a reactant mass remained at the bottom of the crucible. Needlelike leucite crystals were obtained by treating this reactant mass with hot HCl. The effect of the mixing ratio of the raw materials, the heating temperature and the duration of heating at the selected temperature on the formation of needlelike leucite crystals was investigated. When a powder mixture, consisting of Al-2(SO4)(3): SiO2: K2SO4=1.0 :2.8: 1.9 (molar ratio), was heated at 1200 degrees C for 3 h, the obtained needlelike leucite crystals were 1-2 mu m in length and 0.1-0.3 mu m in width. Needlelike leucite crystals were formed by the crystallization of leucite on small mullite crystals obtained by heating, followed by growth of the leucite crystals in a liquid phase of the K2SO4 flux as the main component.