Orthorhombic boron oxide under pressure: in situ study by X-ray diffraction and Raman scattering

TL;DR

This study investigates the high-pressure behavior of orthorhombic boron oxide (ta;-B2O3) using in situ X-ray diffraction and Raman scattering, providing experimental and theoretical insights into its structural and vibrational properties.

Contribution

The paper presents the first in situ high-pressure measurements of ta;-B2O3, including its bulk modulus, vibrational spectra, and isotope effects, supported by ab initio calculations.

Findings

Bulk modulus of ta;-B2O3 is 169 GPa.

All observed Raman and IR bands match theoretical predictions.

Isotopic substitution affects Raman spectra.

Abstract

High-pressure phase of boron oxide, orthorhombic \b{eta}-B2O3, has been studied in situ by synchrotron X-ray diffraction to 22 GPa and Raman scattering to 46 GPa at room temperature. The bulk modulus of \b{eta}-B2O3 has been found to be 169(3) GPa that is in good agreement with our ab initio calculations. Raman and IR spectra of \b{eta}-B2O3 have been measured at ambient pressure, all experimentally observed bands have been attributed to the theoretically calculated ones, and the mode assignment has been performed. Based on the data on Raman shift as a function of pressure, combined with equation-of-state data, the Gr\"uneisen parameters of all experimentally observed Raman bands have been calculated. \b{eta}-B2O3 enriched by 10B isotope has been synthesized, and the effect of boron isotopic substitution on Raman spectra has been studied.