Study of microindentation cracks in bismuth-doped arsenic selenide glasses

The formation of radial cracks from Vickers indentations on the surfaces of both unirradiated and irradiated samples of (As1 − xBix)2Se3 glasses with x ≤ 0.1 is investigated as a function of indentation load P. It was found that radial cracks around indentations are produced on the surfaces of all samples at loads exceeding a particular applied load Pcapp but this threshold load is higher by a factor of 15 to 30 from the value of Pc calculated from the theoretical dependence of ratio c/d of crack length c measured from the center of indentation impression to indentation impression diagonal d on applied load P. By fitting the experimental P(c3/2) data in an expression relating c and P according to expanding cavity for elastic/plastic solid and from a theoretical expression relating load-independent hardness H and threshold load Pc for crack formation estimated from the experimental data of the dependence of c/d on P, the value of indentation fracture toughness KC of As2Se3 glasses, irrespective of Bi content in the samples and their irradiation, was found to be about 0.52 MPa⋅m1/2.

Research highlights
► There is no clear correlation between the observed load Pcapp for the appearance of cracks and Bi content.
► Pcapp somewhat increases upon irradiation of samples.
► The threshold load Pcadd for the visibility of cracks corresponds to diagonal d = from 10 to 15 μm.
► The fracture toughness KC for different samples was determined.