Raman scattering in glassy Li2B4O7

Abstract

Lithium tetraborate is a promising material to be used in the production of solid electrolytes and solid-state batteries. A powerful tool for investigating its structure in the B2O3–Li2O system is Raman spectroscopy. The Raman spectra were investigated using the XploRA PLUS (HORIBA Jobin Yvon) Raman spectrometer at the temperature of T = 300 K within the 70–2000 cm–1 range. The excitation wavelength was 785 nm, the spectral resolution was no worse than 1 cm–1. As a result of the study, we have determined the nature of vibrational modes. We detected a fine structure in the 70–400 cm–1 range, which we found to correspond to normal vibration of the lithium-oxygen structural complexes in the structure of [LiO6] frames, and also vibrations and librations of [LiO6] frame and the BO3 and BO4 groups in the structure of [B4O7] 2– cluster as a whole. In the 400–800 cm–1 range the superposition of vibrations of [LiO4] clusters and [BO4] tetrahedrons takes place, whereas their normal vibrations are detected in the 800–1354 cm–1 range. In the 1300–2000 cm–1 range we observed the manifestation of two-phonon states, the normal vibrations of borate rings, and the symmetric stretching of the BO3 flat triangles, and detected two peaks that have not been observed previously. The obtained results show that the Raman spectra of glassy Li2B4O7 generally display a single-mode behavior and are caused by a combination of vibrations of different types which are interconnected via the frame structure of the glass consisting of complex boronoxygen and lithium-oxygen structural complexes.

Досліджено спектри комбінаційного розсіювання світла у склоподібному тетрабораті літію. Встановлено, що більшість коливальних мод скла Li2B4O7 у межах усередненого порядку зумовлена змішаними модами складних бор-оксигенових та літій-оксигенових структурних комплексів.