Figure 7.

(a) Vickers microhardness distribution of untreated MS-ZnS, annealed MS-ZnS, and Sample #3. (b) Average microhardness values of Samples #1, #2, and #3 obtained by Ga₂S₃-treatement (this work) compared to co-sintered Ga₂S₃-ZnS ceramics (from [14]). The single sphalerite (S) phase and two-phase sphalerite + tetragonal (S + T) domains are both represented in this figure to highlight the difference in hardness improvement one can obtain from cationic substitution (single-phase solute strengthening) and precipitation hardening (presence of two-phases). The latter comes at the expense of transparency due to scattering.