Pressure-Induced Structural Transformations and Electronic Transitions in TeO2 Glass by Raman Spectroscopy

TeO2 glass has been studied by Raman spectroscopy up to the record pressure of 70 GPa. The boson peak frequency cob exhibits a decrease of the partial differential cob/ partial differential P slope at 5-6 GPa and saturates above 30 GPa with a practically constant value up to 70 GPa. Experiment and theory indicate that pressures up to 20 GPa induce the transformation of single Te-O-Te bridges to double Te-O2-Te bridges, leading to a more compact structure, while Raman activity developing at higher pressures around 580 cm-1 signals the increase of Te coordination from 4 to 6-fold. Natural bond orbital analysis shows that double Te-O2-Te bridges favor the s -> d transition and promote the increase of Te coordination through d2sp3 hybridization. This transition leads to the formation of TeO6 octahedra, in strict difference with crystalline TeO2 at the same pressure range, and to the development of a 3D network that freezes the medium range order.

Automated summary

TeO2 glass was studied by Raman spectroscopy up to a record pressure of 70 GPa. The boson peak frequency cob decreased with partial differential cob/ partial differential P slope at 5-6 GPa, and reached a constant value above 30 GPa. The transformation of single Te-O-Te bridges to double Te-O2-Te bridges occurred under pressures up to 20 GPa, resulting in a more compact structure, while Raman activity at around 580 cm-1 indicated the increase of Te coordination from 4-fold to 6-fold at higher pressures.