Liquid Regions of Lanthanum-Bearing Aluminosilicates

The Al₂O₃-SiO₂, La₂O₃-Al₂O₃, and La₂O₃-SiO₂ binary phase diagrams were estimated by Redlich-Kister expression. La_4.67Si₃O₁₃ (=La_4.67(SiO₄)₃O) was introduced to improve the existing phase diagrams. The Al₂O₃-SiO₂-La₂O₃ ternary phase diagram extrapolated by Kohler method was optimized. Then, the liquidus of Al₂O₃-SiO₂-La₂O₃ system at 1600 °C was compared with Al₂O₃-SiO₂-RE₂O₃ (RE = Rare Earth Elements) systems and experimental results in other literature. The high temperature experiments were conducted in the tube furnace at 1500 °C. Then the field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) were employed to verify the calculated liquid region and precipitates phase at 1500 °C. Moreover, the liquidus of binary systems were compared with FactSage results and experiments. The optimized ternary phase diagram shows the relatively reliable region of liquid phase, and it is significant to the seal glass of solid oxide fuel cells and other fields being related to RE containing silicates.