Transparent nanocrystalline pure and Ca-doped MgO by spark plasma sintering of anhydrous nanoparticles

Fully dense nanocrystalline MgO-based ceramics were consolidated by field and pressure assisted sintering (also known as Spark Plasma Sintering) using anhydrous nanosized powders (∼5 nm) prepared by laser ablation and handled in a controlled, water-free environment prior to sintering. The high reactivity of the powders promoted excellent sinterability at relatively low temperatures. Highly transparent specimens were produced by sintering at 0.23-0.28T _m (650°C-800°C) for 15-30 min with good control over the final nanometric grain size. To preserve the nanocrystalline nature of the samples, the high temperature exposure time during sintering was reduced by the application of 300 MPa uniaxial pressure; higher pressure or two-step procedures did not provide extra benefits to densification or microstructural control.