FT-IR study on interaction of hydrogen isotopes with defects in lithium oxide

The existing state of hydrogen isotopes in lithium oxide (Li2O) was studied using Fourier transform infrared absorption spectroscopy (FT-IR). Infrared spectra in Li2O single crystals which were treated by thermal absorption and consequent quenching were observed from room temperature to 773 K. Multiple peaks were observed in the O–D stretching vibration region and these peaks had different dependence on temperature. These peaks were attributed to the stretching vibrations of O–D presenting as LiOD or Li2O–D+ in bulk Li2O with or without defects. Above 623 K, most of the deuterium ions in Li2O exist as Li2O–D+ and the infrared absorption peak for them was observed around 2520 cm−1. The absorbance decrease of this peak during the isothermal annealing was well analysed by a diffusion model. Diffusion behaviour of hydrogen isotopes in Li2O was discussed from the in-situ observation of O–D.