On the structural phase transformations in GexSb40−xSe60 glasses

A correlation between the observed peculiarities in the variation of some physicochemical parameters of GexSb40−xSe60 (x=10, 20, 25, 27, 32, 35) glasses and their structure has been found by studying the average coordination, Z. In particular, the composition dependences of the microhardness and its derivative characteristics (micro-voids volume, their formation energy, and module of elasticity) have shown an extremal behaviour at Z=2.65–2.67. The results on the density and compactness have also indicated the occurrence of an additional feature at the Ge27Sb13Se60 composition having Z=2.67. Furthermore, the increase of the intensity ratio between homopolar and heteropolar Raman bands with Z is accompanied by a break at Z=2.65–2.67. The observed Raman modes have been related to the corresponding bond vibrations and the structure of the glasses studied has been specified. Accepting a tendency towards strong chemical ordering for these glasses, the distribution of the possible chemical bonds has been determined. The obtained defective bond population is confirmed by the experimental Raman data.The established peculiarities at Z=2.65–2.67 have been attributed to structural rearrangements of the backbone of the glasses.