Structure and ferroelectricity of nonstoichiometric (Na_(0.5)Bi_(0.5))TiO_3

摘要

Stoichiometric (Na_(0.5)Bi_(0.5))TiO_3 (NBT) adopts the ABO_3 perovskite structure with the A-site equally occupied by Na~+ and Bi~(3+) ions. However, non-stoichiometric compositions can be synthesized intentionally or unintentionally. To determine the effect of A-site nonstoichiometry on the crystal structure and ferroelectricity of NBT, the composition of (Na_(0.5-x)Bi_(0.5+x))TiO_(3+x) was varied using x = -0.01, -0.005, 0, 0.005, and 0.01. High resolution synchrotron x-ray diffraction and Rietveld refinement revealed that a shift in either direction from x = 0 results in a decrease in the spontaneous ferroelastic strain. Ferroelectric hysteresis and piezoelectric coefficients were found to be optimum in the stoichiometric composition.