MgAl2O4 spinel powder of 5 to 20 nm particle size, was prepared by the hydrolysis-condensation reaction of a heterobimetallic aluminum magnesium n-butoxide modified by polyethylene glycol (PEG). The gel after hypercritical drying yielded a porous aerogel with a density of 0.2 g/cm3. Calcination of the aerogel at 700-degrees-C in air yielded a pure MgAl2O4 powder which could be hot pressed to transparency.