Sub-solidus phase relations and a structure determination of new phases in the CaO–La2O3–TiO2 system

Abstract

Sub-solidus phase relations in the ternary CaO–La2O3–TiO2 system at 1400°C in air were determined. The multi-phase samples were prepared by a solid-state reaction method, whereas the single-phase samples for the structure analysis of selected solid solutions were prepared by a wet-precipitation method in order to provide good homogeneity of the starting mixtures. The phases in the prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The oxides form seven ternary compounds in the equilibrium state, many solid solutions (which extend across a broad concentration region), and a large, single-phase area based on the CaTiO3 solid solution. The structures of several new phases – solid solutions on the tie lines CaTiO3–Ca3La4Ti3O15 and La2TiO5–Ca3La4Ti3O15 – were determined in detail.