Luminescence properties and a substitution defect model for self-reduction of europium ions in silicate Ba(Eu)MgSiO 4 phosphors

Abstract The variations of luminescence properties of silicate Ba(1−x)MgSiO4:xEu phosphors are investigated in view of the structure of the host matrix and different synthetic atmosphere. X-ray powder diffraction patterns, luminescent spectra and electron spin resonance are used to confirm the compound structure and detected the simultaneous existence of both divalent and trivalent europium ions. The results indicate that both Eu2+ and Eu3+ are co-existing in the silicate when synthesized under air atmosphere due to the substitution of Eu3+cations for alkaline earth (Ba2+) triggers the formation of V B a / / vacancies that play the role of electron donor towards E u B a defects. The higher the concentration of V B a / / , the easier the reduction of Eu3+ into Eu2+. The co-doping with higher state chemical elements (i.e., La3+, Zr4+) helps a lot in increasing the concentration of Eu2+cations at the expense of Eu3+ ions in the Ba(1−x)MgSiO4:xEu phosphors. The energy transfer between Eu2+ cations in different sites within the BaMgSiO4 host matrix is also observed and its mechanism is charged by multipolar interaction.