Local coordination environments and momentum distribution of hydride-ions in perovskite type oxyhydrides

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. The current understanding of the hydride-ion dynamics in these materials is primarily based on our results from quasielastic neutron scattering (QENS) and inelastic neutron scattering (INS) experiments on BaTiO3-x-yHx◻y (BTO) (◻ denoting oxygen vacancies) and SrTiO2.81H0.13◻0.06 (STO). STO showed local and fast hydride-ion dynamics, while BTO showed slow and long-range diffusion of hydride-ions. Since STO and BTO differ in the A site ion (Sr/Ba) and oxygen vacancy concentrations, these results suggest that the nature of hydride-ion dynamics is highly dependent on local structure of the oxyhydride. In order to shed more light on the local structural differences between BTO and STO, especially in regard to the vibrational properties of the hydride ions, we wish to investigate the nuclear kinetic energy (NKE) of the hydride-ions, which may affect considerably the nature of the diffusion. For that purpose, we would like to use the spectrometer VESUVIO for a neutron Compton scattering (NCS) experiment on BTO and STO, and ask for 7 days of beamtime with this instrument.