Photoluminescence investigations of Li2SiO3:Ln (Ln=Er3+, Eu3+, Dy3+, Sm3+) phosphors
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In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li2SiO3) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li2SiO3 compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er3+ luminescence at 1.54 mu m arises from a sharp atomic-like radiative transition between the I-4(13/2) state and the I-4(15/2) state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm3+ emission characteristics corresponding to the some (4)G(5/2) -> H-6(j) (j = 5/2.9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the D-5(0) -> F-7(j) (j similar or equal to 0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive (D-5(0) -> F-7(2)) transition of Eu3+ indicates the inversion antisymmetry crystal field around Eu3+ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy3+ emission characteristic due to the F-4(9/2) -> H-6(13/2) transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material. (C) 2012 Elsevier B.V. All rights reserved.