On the quantification of hydrogen in lithium metal oxides

Hydrogen incorporation during crystal growth or other treatment has attracted research interest for a long time, but inconsistent literature data exist about the bulk hydrogen concentration in the lithium metal oxides Li M O 3 with M = Nb and Ta. Hydrogen binds to oxygen and forms hydroxyl groups (OH − ), which can be easily detected optically by FT-IR spectroscopy. However, this method cannot determine an absolute hydrogen concentration. With a reliably characterised concentration reference, a calibration for the fast and non-destructive FT-IR spectroscopy could be obtained. In this study, the hydrogen contents of as-grown and hydrogen-doped congruent and near-stoichiometric Li M O 3 crystals were investigated by elastic recoil detection analysis (ERDA), carrier gas hot extraction (CGHE), 1 H magic angle spinning nuclear magnetic resonance ( 1 H MAS NMR) and hydrogen microscopy via proton-proton (p-p) scattering. However, not every method is suitable for the investigation of hydrogen in the Li M O 3 host lattices. Based on p-p scattering, the A / c H calibration factors for FT-IR spectroscopy can be specified with (4.52 ± 0.58) × 10 −17 cm and (6.46 ± 0.96) × 10 −17 cm for LiNbO 3 and LiTaO 3 , respectively. This article presents different hydrogen sensitive methods to determine the bulk hydrogen content in Li M O 3 ( M = Nb, Ta).