High-precision measurements of the compressibility of chalcogenide glasses at a hydrostatic pressure up to 9 GPa

Abstract

The volumes of glassy germanium chalcogenides GeSe2, GeS2, Ge17Se83, and Ge8Se92 are precisely measured at a hydrostatic pressure up to 8.5 GPa. The stoichiometric GeSe2 and GeS2 glasses exhibit elastic behavior in the pressure range up to 3 GPa, and their bulk modulus decreases at pressures higher than 2–2.5 GPa. At higher pressures, inelastic relaxation processes begin and their intensity is proportional to the logarithm of time. The relaxation rate for the GeSe2 glasses has a pronounced maximum at 3.5–4.5 GPa, which indicates the existence of several parallel structural transformation mechanisms. The nonstoichiometric glasses exhibit a diffuse transformation and inelastic behavior at pressures above 1–2 GPa. The maximum relaxation rate in these glasses is significantly lower than that in the stoichiometric GeSe2 glasses. All glasses are characterized by the “loss of memory” of history: after relaxation at a fixed pressure, the further increase in the pressure returns the volume to the compression curve obtained without a stop for relaxation. After pressure release, the residual densification in the stoichiometric glasses is about 7% and that in the Ge17Se83 glasses is 1.5%. The volume of the Ge8Se92 glass returns to its initial value within the limits of experimental error. As the pressure decreases, the effective bulk moduli of the Ge17Se83 and Ge8Se92 glasses coincide with the moduli after isobaric relaxation at the stage of increasing pressure, and the bulk modulus of the stoichiometric GeSe2 glass upon decreasing pressure noticeably exceeds the bulk modulus after isobaric relaxation at the stage of increasing pressure. Along with the reported data, our results can be used to draw conclusions regarding the diffuse transformations in glassy germanium chalcogenides during compression.