Hydride-ion dynamics in a Barium Titanate Perovskite Oxyhydride

Perovskite type oxyhydrides, ATiO3-xHx, A = Sr, Ba, with x < 0.6 [1], are a novel class of hydride-ion (H-) conducting materials that may find diverse applications in the fields of catalysis, topochemical synthesis, and electrochemistry, but fundamental questions surrounding the mechanism of hydride-ion conductivity remain to be answered. The current understanding of the hydride-ion dynamics in these materials is primarily based on our results from quasielastic neutron scattering (QENS) experiments on BaTiO3-x-yHx◻y (◻ denoting oxygen vacancies) where we observed a temperature-dependent diffusion mechanism characterized by hydride-ion jumps between nearest-neighbor oxygen vacancies. In addition, we observed in SrTiO2.81H0.13◻0.06 fast and localized hydride-ion motions, already at low temperature (100 K), contrasting with the slow and long-range mechanism so far reported with BaTiO3-x-yHx◻y. However, the QENS signal is weak and hampered by a large elastic contribution from the disordered perovskite host lattice, and its the analysis is difficult. In order to shed more light on the observed dynamics of SrTiO2.81H0.13◻0.06, and investigate the effect of the A site ion (Sr/Ba), we propose a QENS study of BaTiO2.81H0.13◻0.06 on the spectrometer LET using polarization analysis as a mean to separate the spin-incoherent scattering from the isotopic nuclear disorder scattering, and from the coherent scattering at Bragg peak positions.