Effect of Ba Nonstoichiometry in Bax(Zr0.8Y0.2)O3−δ on Population of 5‐Coordinated Y

The local environments of Y in the Y-substituted BaZrO3 of the starting compositions of Bax(Zr0.8Y0.2)O3−δ (x = 0.97, 1.0, 1.03, and 1.06) were analyzed by 89Y magic angle spinning NMR spectroscopy. The result showed a strong population dependence of 5-coordinated Y3+ ions mostly at the B site on the Ba contents. The enhancement of Ba contents by 9 at% (from 0.97 to 1.06 in the starting Ba contents) in a nominal composition increased the amount of 5-coordinated Y3+ ions from 35% ± 7% to 49% ± 5%, suggesting the importance of maximizing the Ba contents to populate more oxygen vacancies which is related to the concentration of protons incorporated during the hydration process. The wide variation in the lattice parameter of yttrium-substituted BaZrO3 perovskite materials in previous reports was reinterpreted with the variation in the Ba contents resulting from the evaporation of BaO during the sintering processes. Y3+ ions were confirmed to replace mainly the Zr4+ ions, as expected, and a tendency of oxygen vacancy clustering near the Y3+ ions was discussed.