Vibrational dynamics of indium-substituted barium zirconate oxyhydrides

Perovskite type oxyhydrides are a class of hydride-ion (H-) conducting compounds that find applications in for example catalysis and electrochemistry. A recent study [Toriumi et al. Chem. Mater. 34 7389-7401 (2022)] have, somewhat surprisingly, found that barium indate zirconate, BaZr0.5In0.5O2.75, a material which has been studied well in the past due to its proton conductivity in a wet atmosphere, can be converted into an oxyhydride via heating under an hydrogen gas atmosphere. The resulting phase yields a stoichiometry BaZr0.5In0.5O2.25H0.5, with indium present as In(II) and hydrogen present as hydride ions. Here, we propose to investigate the local structure of hydride ions with INS in a series of oxyhydride prepared by hydrogen gas reduction with varying indium content. A particular interesting question surrounds the possible hydride-ion sites in the structure. Rietveld analysis of neutron diffraction data in the previous study yielded two possible hydride-ion sites, i.e. (i) in an oxygen vacancy, or (ii) in an interstitial site. Interestingly, such interstitial hydride ions have never been observed before in oxyhydrides. We therefore propose to directly investigate the local hydride environment using INS.