A crystal structure was proposed for reduced barium titanate, BaTiO3–δ, with δ equal to about 0.33, formed during the degradation of Ni–BaTiO3 X7R multilayer ceramic capacitors. High-resolution transmission electron microscopy and selected-area electron diffraction were used in combination with computer simulations to show that O vacancies accrete on every third pseudocubic {111} plane, resulting in a cell with space group P3m1. Additionally, from electron energy loss spectroscopy, it was proposed that Ti4+ was reduced to Ti3+ as a mechanism of charge compensation within O-deficient octahedra.

Vacancy Ordering in Reduced Barium Titanate. D.I.Woodward, I.M.Reaney, G.Y.Yang, E.C.Dickey, C.A.Randall: Applied Physics Letters, 2004, 84[23], 4650-2