Dependence of ZnO-based Phosphor Spectral Emission on UV and X-ray Excitation Pulse Width

Emission from lanthanide or transition metal-doped ceramics—phosphors—is thermographic due to competition between radiative and non-radiative processes observed after excitation from either a UV (non-ionizing) or x-ray (ionizing) source. The mechanisms of excitation, non-radiative relaxation, and emission vary between the two excitation strategies: UV excitation causes emission from internal transitions of valence electrons that can decay via processes such as charge transfer states, and x-ray excitation causes core electron ejection and emission via electron-hole recombination pairs that may relax via phonon production. This work explores the effects that various ionizing and non-ionizing excitation sources have on the spectral properties of ZnO:Zn and ZnO:Ga. Results indicate that the spectral properties of ZnO:Ga remain invariant between continuous synchrotron x-ray excitation and pulsed UV laser excitation. However, ZnO:Zn spectral properties are shown to vary between sources of differing pulse durations. Spectra produced by this phosphor from a continuous synchrotron x-ray beam match those obtained from continuous UV excitation using a UV LED. The intensities of the present spectral lines vary dramatically from those observed for ZnO:Zn excited using a pulsed UV laser system. The implications of this variance in spectral properties of ZnO:Zn due to excitation pulse duration are discussed. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-14571 A