Y, Lu, La cation substitution for luminescence tuning in MSi2N2O2:Eu2+ (M=Ca, Sr, Ba) phosphors

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Abstract
06-179 Malgorzata Maria Sopicka-Lizer Sopicka-Lizer, M.M.(Silesian University of Technology); Michalik, D.(Silesian University of Technology); Pawlik, T.(Silesian University of Technology); Krzywda, P.(Silesian University of Technology); MSi2N2O2:Eu2+ (M=Ca, Sr, Ba) oxynitride powders are useful phosphor hosts for application in efficient white light after excitation by a blue light emitting diode. Both, cation substitution and oxygen to nitrogen ratio are tried to shift emission spectrum and/or to optimise luminescent properties. This paper deals with substitution of trivalent M cations for divalent ones with simultaneous nitrogen for oxygen cross-substitution. Trivalent cations, optically passive, were chosen on the basis of an ionic size similarity in order to minimise crystal lattice stresses after formation of solid solution. Differences in cation’s electronegativity in the range of 0.89 (Ba) to 1.27 (Lu) with simultaneous nitrogen presence in the proximity of optical activator were expected to tailor luminescence properties of modified oxynitride phosphors. It has been found that size effect of M cation was crucial in formation of solid solution since precipitation of the side phase was observed in barium oxynitride while calcium oxynitride formed excellent solid solution with all substituting cations. Both, wavelength of excitation and emission spectra were red-shifted, as expected from higher nitrogen dissolution in oxynitride matrix. The highest quantum yield was observed for samples modified with lutetium. Some discussion on the observed modification was provided.
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