ZnAl2O4: Cr3+ (Co2+) nanopowders were prepared by hydrothermal method and annealed at
various temperatures. The samples were characterized by X - ray diffraction, transmission electron
microscopy, photoluminescence and photoluminescence excitation spectra. The results show that crystal
structure and optical properties of the samples were affected by heat treatment regime. When annealing
temperature increased, crystal structure of the samples became better. Optical spectra of the ions Cr3+ are
sensitive to crystal structure of the host lattice. Electron transitions difference in absorption and radiation
processes between the samples ZnAl2O4: Co2+ unannealed and annealed at high temperature was
investigated. ?? 2009 IOP Publishing Ltd.
