Inverse Hall–Petch effect in nanostructured ZnS

Vickers microhardness of compacted nanoparticles of ZnS of average grain sizes 3–12 nm was studied for different compaction pressures. The hardness was found to increase rapidly with load for smaller values of the load and then to become practically independent of load. The microhardness was found to increase with increase in grain size showing inverse Hall–Petch relation in the present study.