Permanent Ge Coordination Change Induced by Pressure in La 2 O 3 –B 2 O 3 –GeO 2 Glass
Résumé
In this study, we report the results of an in situ X‐ray absorption spectroscopy investigation of the La 2 O 3 –B 2 O 3 –GeO 2 (LBG) glass compressed in a diamond anvil cell until 17 GPa at ambient temperature. A pressure‐induced coordination change of germanium from fourfold to sixfold is shown here. The analysis of Ge K‐edge X‐ray absorption near‐edge structure spectra supports a model of mixing of fourfold and sixfold coordinated Ge sites during the compression/decompression cycle. This transformation proves to be irreversible: about 25% of sixfold coordinated Ge still exists at ambient pressure. This phenomenon underlines a polymorphism property of the LBG glass, whose origin lies in the complexity of composition.