As2Te3 glass under high hydrostatic pressure: Polyamorphism, relaxation, and metallization

Abstract

High-precision measurements of the specific volume and electrical resistivity of $\mathrm{A}{\mathrm{s}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ glasses are performed under hydrostatic pressures up to 8.5 GPa. A smooth transformation and logarithmic relaxation of the density is observed at pressures higher than 1 GPa. The softening of the effective bulk modulus and the relaxation rate have a sharp maximum at 2.5 GPa, which is indicative of the existence of polyamorphism. At pressures above 4.5 GPa, a new relaxation process begins. During decompression, the pressure dependence of the compressibility exhibits a kink near 4 GPa. The electrical resistivity decreases by almost 8 orders of magnitude, most sharply in the range of 2--3.5 GPa (by 3 orders of magnitude). Smooth metallization occurs at a pressure of 5 GPa; the resistivity decreases to a value of $1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ at 8.1 GPa. Under decompression, the electrical resistivity exhibits a hysteresis and returns to values 3 orders of magnitude smaller than the initial one. The volume and electrical resistivity under normal conditions relax to quasiequilibrium values in several months. The relaxed glasses with a smaller chemical disorder have a lower electrical resistivity. The results together with the data on the structure and dynamics in $\mathrm{A}{\mathrm{s}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ glasses allow conclusions on the mechanism of pressure-induced transformations.