Microstructural changes in (1 - X)Nd_2/3TiO₃- xNdAlO₃ system

Microstructure studies on the (1 - x)Nd_2/3TiO ₃-AdAlO₃ (NTNA) system were carried out using transmission electron microscopy. The presence of Nd₂Ti₂O₇ and Nd₄Ti₉O₂₄ phases in pure Nd _2/3TiO₃ is confirmed from electron diffraction patterns. At x = 0.1, the ordering due to A-site vacancies is confirmed by the presence of antiphase boundaries and (1/2)(100) superlattice reflection. As x increases, the degree of ordering decreases and finally disappears at x = 0.7. The tilting of oxygen octahedra is demonstrated by the presence of the ferroelastic domains in the matrix and the (1/2)(111) and (1/2)(110) superlattice reflections in selected-area electron diffraction patterns. In the NTNA system of x = 0.1, both the antiphase and inphase tilting of oxygen octahedra are involved; however, in the range of x from 0.5 to 1.0, only the antiphase tilting of oxygen octahedra is observed due to the presence of the (1/2)(111) superlattice reflection and ferroelastic domains. The variations in the measured dielectric properties of NTNA (dielectric constant and Q · f) are consistent with those in the dielectric properties of the (1 - x)La_2/3TiO₃-xLaAlO ₃ (LTLA) system obtained by Lee et al.