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The experimental results of a systematic investigation of the microhardness of two systems of metal-modified arsenic
chalcogenide glasses: Xx(As2S3)100−x (x = 0 or 15, and X = Ag and AgI) and As2Se3 without and with 0.5 at.% RE (RE = Nd,
Sm, Ho and Er) for applied indentation load ranging from 0.005 to 1 N are described and discussed. It was found that, with
an increase in load P, for both systems the microhardness HV first increases, then decreases showing a maximum hardness
Hmax, and finally increases again after attaining a minimum hardness Hmin. Analysis of the experimental data on hardness
HV as a function of indentation diagonal d according to the relation: H = H0(1+d0/d), where H0 is the load independent
hardness and d0 is a constant, revealed that: (1) doping substances lead to the softening of As2S3 samples and hardening
of As2Se3 samples, and the hardening of the matrix may be attributed to the size of doping substance, (2) formation of
cracks in chalcogenide glasses follows the general concepts of fracture mechanics and their generation depends only on
the basic glass matrix but is not affected by dopants and their chemical nature, and (3) the load-independent indentation
microhardness H0 of a sample may be determined only from indentation data obtained in the load interval where HV
decreases with an increase in applied P.
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