Low-temperature high-pressure preparation of transparent nanocrystalline MgAl2O4 ceramics

Transparent MgAl2O4 spinel nanoceramics have been sintered at relatively low-temperature (500–700°C) under high pressure (2–5GPa) using a hydrostatic press with high-temperature-calcined nanopowders. The morphology, nanostructure, optical property, and density of ceramics were analyzed by scanning electron microscopy, transmission electron microscopy, UV-VIS-IR transmission spectrum, and Archimedes draining method. The average grain size (<100nm for all samples sintered) depends on the sintering pressure and temperature. The nanoceramics are highly transparent even though their relative densities are all less than 99%, due to the low or negligible light scattering from the nanosized grains and pores.