Mechanisms of ZnO luminescence in the visible spectral region

Existing models of zinc oxide luminescence in the visible spectral region are considered and comparatively analyzed. Experiments are performed with ceramics obtained from initial ZnO powder and ZnO powders annealed in vacuum (ZnO-vac) and in air (ZnO-air). The luminescence characteristics of the ceramics, namely, emission and excitation spectra, kinetics, and temperature stability, are studied. The ZnO-vac ceramics exhibits green luminescence caused by neutral oxygen vacancies. The luminescence of ZnO-air ceramics is shifted to the red and is presumably related to residual lithium impurity. The ceramics differ in the luminescence excitation spectra, time characteristics, and temperature stability.