Effect of Sr and Ca substitution of Ba on the photoluminescence properties of the Eu2+ activated Ba2MgSi2O7 phosphor

Abstract

The effects of Sr and Ca substitution of Ba on the Ba1.98-xSrx(Cax)MgSi2O7:Eu2+ photoluminescence properties have been investigated. The physical mechanisms for the photoluminescence variations are discussed. With Rietveld refinement method, the crystal structure of Ba1.98MgSi2O7:0.02Eu2+ and the lattice parameters of Sr and Ca substituted phosphors were refined. The emission band shift, the photoluminescence intensity variation, the phosphor chromaticity evolution, the Eu2+ lifetime distribution and the thermal stability elevation were investigated. With Sr and Ca substitution, the cell is shrinks. The cell shrinkage is resulting in the increase of the Eu2+ 5d electron crystal field splitting intensity, which is the reason for the emission band shift towards the long wavelength band. The photoluminescence intensity is increased firstly and then decreased. The intensity variation is the competitive result between the increase of the crystal structure rigidity and the rise of the lattice defect. The correlated color temperature can be cut down and the color purity can be adjusted. The photoluminescence life time of Eu2+ is raised firstly and then decreased. For Sr and Ca substitution, the thermal stability can be elevated. With the forbidden band gap calculation, the reason for the thermal stability elevation was investigated that for the substituted phosphors the forbidden band gap is enlarged and then limits the Eu2+ 5d self-ionization from the splitting levels to the conduction band. This work reveals that the Sr and Ca substitution of Ba can elevate the Ba1.98-xSrx(Cax)MgSi2O7:Eu2+ photoluminescence properties and improve the applications for the White Light Emitting Diode.