Structural defects and acidic and basic sites in sol-gel MgO

MgO prepared with the sol-gel technique had crystalline structure defects, obtained from X-ray powder diffraction and crystalline structure refinement, that correlated with its acidic and basic sites. The acidic sites, measured by adsorbing pyridine and NH₃, were found when brucite and MgO coexisted, which only occurred after annealing the sample at 673 K. Two different basic sites, measured by adsorbing CO₂, were present in a total concentration of about 10²¹ sites per gram. These sites correlated to the presence of magnesium vacancies in MgO crystal. Both basic site and magnesium vacancy concentrations diminished when the sample annealing temperature was increased.