A clear effect of charge compensation through Na+ co-doping on luminescent properties of new CaGa4O7:Nd3+

Abstract

Two series of new calcium gallates: Ca1−xNdxGa4O7 and Ca1−2xNdxNaxGa4O7 (x = 0.001, 0.01, 0.03, 0.05, 0.1) were synthesized by a modified Pechini method and their optical properties at 298 K and 77 K were investigated. Relatively intense characteristic Nd3+ luminescence in IR region with maximum located at around 1075 nm was observed in all samples on direct excitation into f-f transitions. The effects of activator concentration and Na+ co-doping on morphology, luminescence and absorption spectra as well as decay kinetics were studied in details. The results show that both, the Nd3+ concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of activator concentration showed an increasing distortion of the local symmetry of Nd3+ with raising activator content due to certain defects created in the crystal lattice. On the other hand co-doping with Na+ ions led to smaller disturbance of Nd3+ ions local symmetries and significantly enhanced luminescence. Analysis of decay kinetics of both series of compounds showed smaller concentration quenching in charge compensated with Na+ ions powders due to smaller clustering of Nd3+ ions in CaGa4O7 lattice.