The spectroscopy of hydride in single crystals of SrTiO3 perovskite.

ABSTRACT

Under reducing conditions, SrTiO3 perovskite can exchange up to 20% of its O2- ions for H- (hydride), greatly influencing its material properties. This not only presents intriguing possibilities for material design, but also for hydrogen sequestration in the deep earth, where perovskite-structured minerals are abundant. However, uncertainties remain surrounding hydride incorporation in SrTiO3, including details of the hydride structural state, and how hydride interacts with the broader defect chemistry of SrTiO3. Additionally, experimental studies of hydride in SrTiO3 and other perovskites may face analytical limitations. The most common methods for characterizing hydride, namely 1H NMR, may not be suitable in all experimental contexts, including materials with relatively low hydride concentrations and in situ high-pressure, high-temperature experiments. Here, we present an investigation of hydride in single crystals of SrTiO3 focused on detailed spectroscopic measurements. Through a combination of density functional theory (DFT)-assisted Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy, we observe structural hydride and its effects on the electronic transitions in SrTiO3. These results are compared directly against 1H NMR. We find that, although hydride is sometimes difficult to identify via FTIR, infrared spectroscopy is significantly more sensitive to hydride than 1H NMR. We also find that DFT makes accurate predictions about the spectroscopic behavior of hydride in SrTiO3, pointing to the value of ab initio techniques in future studies.