Single crystals of MgO were synthesized using a simple precipitation method with no templates. The
magnesium hydroxide was synthesized at 25 C or 100 C by the precipitation of magnesium nitrate solution,
aged at room temperature or 100 C. Precipitation temperature had a great influence on the morphology
in the synthesis of magnesium oxide. The N2 physisorption, XRD and electron microscopic
(SEM/TEM, HRTEM) analysis associated with the electron diffraction reveal the different morphological
structures and pores of MgO synthesized with different synthesis methods. Precipitation at 25 C generated
macroporous MgO with plate-like crystals. However, the change of precipitation temperature to
100 C generated mesoporous single crystalline MgO, and the stabilization and growth of MgO(111)
planes (with d-spacing of 0.244 nm) was observed. The formation of mesopores and single crystallinity
of MgO synthesized by the precipitation at 100 C were retained even after calcination at a temperature
of 800 C for 5 h.