Deformation and Cracking in Ge–Sb–Se Chalcogenide Glasses During Indentation

Deformation and cracking behavior of Ge–Sb–Se binary and ternary chalcogenide glasses of varying average covalent coordination number, 〈 r 〉, was studied by indenting with Vickers and Brinell microindenters using static and recording machines, and subsequent analysis using a non-contact profilometer. Vickers-produced cracks were the smallest around the GeSe₄ composition (〈 r 〉=2.4) after unloading, hence the indentation toughness was a maximum and the brittleness a minimum at 〈 r 〉=2.4. Brinell-created pond (crater) depth, the mound (pile-up) height, and the radial fractures originating from the mounds displayed minima in the binaries, presumably due to maximized elastic recovery around 〈 r 〉=2.4. Consequently, Brinell hardness computed from the unloaded depth ( H _BD) showed a maximum around GeSe₄. The maximized elastic recovery around GeSe₄ is consistent with Phillips' optimized connectivity arguments. GeSe₄ resembles the "anomalous" SiO₂ glass for deformation and cracking behavior. Surprisingly, many of the extrema were nearly non-existent in the ternary glasses. The apparent contrast to the binary glasses is not understood.