Spark plasma sintering and mechanical behavior of magnesia–yttria (50:50 vol.%) nanocomposites

Fully dense magnesia–yttria (50:50 vol.%) nanocomposites with average grain sizes ranging from 125 to 223 nm have been prepared by spark plasma sintering. Grain growth is mainly dominated by grain boundary diffusion. A coarser grained sample prepared by post-sinter annealing was also studied for comparison. Samples with finer grain sizes exhibit superior mechanical properties, including higher microhardness and improved nanoscratch behavior. The fracture toughness, 1.5 MPa m1/2 on average, is independent of the average grain size of the samples.