Dependence of MgGa2O4:Co2+photoluminescence on temperature and impurity concentration

Polycrystalline samples of MgGa 2 O 4 doped with 0.1 and 1.0% of Co 2+ ions were produced by ceramic methods and investigated by x-ray diffraction and luminescence spectroscopy. Emission data at room temperature and 77 K, as well as transition lifetimes obtained by the phase-shift method, are presented. The emission is attributed to 4 T 1 ( 4 P) → 4 A 2 ( 4 F) of Co 2+ ions in tetrahedral sites. The excitation spectra are associated with 4 A 2 ( 4 F) → 2 A 1 ( 2 G), 4 A 2 ( 4 F) → 2 E( 2 G) and 4 A 2 ( 4 F) → 4 T 1 ( 4 P) electronic transitions. The crystal field Dq and Racah parameter B were obtained from the spectra and Tanabe-Sugano energy level diagram. The highlights of the present work are the relatively simple sample obtention process as well as its reproducibility and the high photoluminescence quantum efficiency (near to 1.0) together with the intense and broad emission band which make the MgGa 2 O 4 a very attractive material for use as tunable media.