Cathodoluminescence and transmission electron microscopy studies in thermochemically reduced MgO:Ni crystals

The effects of thermochemical reduction in nickel-doped MgO crystals have been investigated by cathodoluminescence and transmission electron microscopy. Two cathodoluminescence bands at 410 nm (3.0 eV) and 490 nm (2.5 eV) have been observed. The former band appears only in specimens after reducing treatments and is attributed to anion vacancies. The latter is associated with Ni2+ transitions 1T2g→3A2g. The results are analyzed on the basis of the emission from F-type centers and Ni2+ ions. Transmission electron microscopy confirms the presence of precipitate groups as well as pyramids in specimens after thermochemical reduction.