High-Precision Studies of the Compressibility and Relaxation of g-As2S3 Glasses at High Hydrostatic Pressures up to 8.6 GPa

Abstract

The high-precision volume measurements of the g-As2S3 glass have been performed at high hydrostatic pressures up to 8.6 GPa, and room temperature. The glass behaves elastically during compression only at pressures up to 1.5 GPa; at higher pressures, a smooth transformation and inelastic density relaxation (logarithmic in time) take place. In the initial segment, the bulk modulus is B = 13.5 ± 0.15 GPa and its pressure derivative is dB/dP = 6.2 ± 0.2. When pressure increases further, the relaxation rate passes through a maximum at 4 GPa, which is accompanied by a bulk modulus plateau, and then decreases and remains noticeable up to the maximum pressure. When pressure decreases, inelastic behavior and the reverse transformation are observed at pressures below 4 GPa. After pressure release, the g-As2S3 glasses have a residual densification of about 3% and their optical properties differ substantially from the initial ones. The glass density relaxes to a quasi-equilibrium value in several months under normal conditions. The kinetics of the Raman spectrum and the optical absorption edge of the glasses during relaxation is studied under normal pressure. The data on compressibility of glasses and comparative Raman studies of initial and compacted glasses show that at pressures up to 9 GPa, there is a strong increase in chemical disorder in the glass, while there is no significant change in the coordination number.