Monochromatic blue-green and red emission of rare-earth ions in MgGa2O4 spinel

Pr3+-activated blue-green phosphor and Eu3+-activated red phosphor hosted in MgGa2O4 spinel have been prepared by a gel-assisted high-temperature calcination process, respectively. Both anion and cation vacancies in the host were formed by decreasing the Mg concentration in the reaction source. The induced vacancies provide possibility of the accommodation of the doped rare-earth ions with larger atomic size in the highly symmetrical spinel structure. Due to the efficient energy transfer from the spinel host to the sole 4f sub-level of the doped rare earths, monochromatic emissions with high efficiency can be obtained to allow the phosphors to find applications in solid-state laser device and other phosphors excited under low energy. The corresponding spectroscopic transition mechanism has been proposed in this work.