Microstructure characterization of the (1-x)La_2/3TiO₃·xLaAlO₃ system

Microstructural characterizations on the (1-x)La_2/3-TiO₃·xLaAlO₃ (LTLA) system were conducted using transmission mission electron microscopy. The presence of La₂Ti₂O₇ and La₄Ti₉O₂₄ phases in pure La_2/3TiO₃ is confirmed by the electron diffraction pattern. When x = 0.1, the ordering due to the A-site vacancies could be confirmed by the presence of antiphase boundaries (APBs) and 1/2(100) superlattice reflection. As x increases, the ordering decreases and finally disappears when x = 0.6. The tilting of oxygen octahedra could be demonstrated by the presence of the ferroelastic domains in the matrix and 1/2(111) and 1/2(110) superlattice reflections in selected area electron diffraction patterns. In pure LaAlO₃, only the antiphase tilting of oxygen octahedra is present due to the presence of 1/2(111) superlattice reflection. In the LTLA system of x = 0.1, both the antiphase and in-phase tiltings of the oxygen octahedra are involved; however, in the range of x from 0.3 to 0.9, the antiphase tilting of oxygen octahedra has appeared. The growth of the ferroelastic domains is influenced by the APBs in the matrix.