Effect of calcination temperature on lattice defects in impure magnesium oxide

The crystallite size and the strain of powdered MgO prepared by decomposing magnesium carbonate in the range 600–1300°C were measured in [100] and [111] crystallographic directions by analyzing the X-ray line broadening. The Warren and Averbach multiple order method was used. The results showed that the crystallite size and the strain are anisotropic. The lattice parameter was calculated from the centre of gravity of the k_α1 line profile of all planes using Wagner's extrapolation method. The changes in the density of the powdered samples and the changes in the unit cell constant showed that the Schottky defects are probably present at low firing temperatures and there are adsorbed contaminant agents on the primary surfaces of the crystallites. The impurities affected the properties of the polycrystalline material. Their effects were very evident in the magnetic susceptibility values, in the sudden increase of the crystallite size above 1000°C and in the high value of the strain at that temperature.