High-temperature refractory ceramics and catalysts such as MgM2O4 (M= Cr, Fe) are produced conventionally via energy-intensive solid-state syntheses (using 0.44-10 GJ electricity for sintering per ton oxide, equivalent to combustion of 48-1088 kg coal per ton oxide). This article reports rapid production of 17 +/- 2 mol% MgFe2O4 and 8.6 +/- 0.9 mol% MgCr2O4 after 30 min at 1200 degrees C employing 0.82 kW m(-2) sunlight concentrated at a geometric ratio of about 900 m(2) m(-2) using a Fresnel lens. Solar radiation promotes the diffusion-limited ferrite formation (42 +/- 5 mu mol MgFe2O4 per mol Fe2O3 s(-1) vs. 26 +/- 3 mu mol mol(-1) s(-1) in absence of sunlight) while the transition metals promote the reduction of Mg2+. The nanocrystalline and macroporous spinel has a specific surface area of 9.7-11.9 m(2) g(-1) (in the order of sal-gel synthesis methods) and is stable under extreme conditions, i.e., high temperature, solar radiation, and reducing agents. (C) 2014 Elsevier B.V. All rights reserved.