Synthesis and characterization of Mg₂SiO₄:Tb³⁺, Eu³⁺ phosphors for white light generation

Abstract

The effect of Eu³⁺ codoping on the structural, morphological, and optical properties of Mg₂SiO₄:Tb³⁺ was investigated. The phosphor powders were synthesized by changing the molar concentration of Eu³⁺ at a fixed Tb³⁺ content of 5 mol% by using a conventional solid-state reaction. The X-ray diffraction patterns revealed that the crystal structure of all the phosphors, irrespective of the Eu³⁺ and the Tb³⁺ contents, showed an orthorhombic structure, and the surface morphology exhibited pebble-like crystalline grains. The emission spectra of Eu³⁺ and Tb³⁺-codoped Mg₂SiO₄ phosphors under an ultraviolet excitation of 252 nm consisted of one intense red band at 619 nm and five weak bands at 448, 488, 598, 658, and 707 nm originating from the transitions of Eu³⁺, in addition to the several emission bands located at 492, 552, 592, and 628 nm arising from the transitions of Tb³⁺. As the Eu³⁺ content was increased, the intensity of the main green emission band at 552 nm decreased markedly and disappeared at 10 mol% Eu³⁺, when complete energy transfer from Tb³⁺ to Eu³⁺ was observed. The results suggest that the emission wavelength and the luminescent intensity of the phosphors can be tuned by modulating the Eu³⁺ and the Tb³⁺ contents incorporated into the host matrix.