Distribution, structures and nonlinear properties of noncentrosymmetric titanates

The difference has been revealed between the statistical distributions of centrosymmetric and noncentrosymmetric titanates over crystal symmetry systems. Space formations of Ti–O polyhedra has been analyzed for 52 noncentrosymmetric titanates. The type of Ti–O polyhedra space formations is dependent on the stoichiometric ratio, SR = n(O)/ n(Ti), where n(O) is the number of oxygen and n(Ti) is the number of titanium atoms in formal composition of the compound. Individual (Ti–O) polyhedra are found for SR ≥ 3.5 (SR ≥ 6 for octahedra), chains and layers of the polyhedra exist in the range stoichiometric ratio, SR = 3.5–7.0. Only framework formations are possible at SR ≤ 3.5.