ISOTHERMAL SECTION OF THE Al2O3–TiO2–La2O3 PHASE DIAGRAM AT 1400 °C

Abstract

Isothermal section of the Al2O3–TiO2–La2O3 phase diagram at 1400 °C is constructed for the first time. It is the part of systematic investigations of Al2O3–TiO2–Ln2O3 (Ln = lanthanides, Y) systems. The 1400 °C was taken as the temperature, at which no liquid is expected in the system. Samples were prepared by a chemical method. Samples were annealed in air at 1400 °C for 80 hour sand cooled in the furnace. Phases in the samples were determined by XRD analysis. New phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of six narrow two-phase and seven three-phase regions. Triangulation of the system is determined by the phase La2Ti2O7, which is in equilibrium with compounds Al2TiO5, LaAlO3 and system components TiO2 and Al2O3. Formation of phases La4Ti9O24, La2Ti3O12 and La2TiO5 in binary boundary system TiO2–La2O3 causes the appearance of partially quasibinary sections Al2TiO5–La4Ti9O24, Al2TiO5–La2Ti3O12 and LaAlO3–La2TiO5. The obtained results make a significant contribution to the understanding of interactions between the components in the system studied. The system includes binary compounds with high electro-optical, ferroelectric, piezoelectric, photocatalytic properties, mikrowave dielectric ceramic. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–La2O3 system.