Crystal structure and luminescence properties of (Ca _2.94-xLu_xCe_0.06) (Sc_2-yMg _y)Si₃O₁₂ phosphors for white LEDs with excellent colour rendering and high luminous efficiency

Lu-modified (Ca_2.94-xLu_xCe_0.06)( Sc _2-yMg_y)Si₃O₁₂ (CLSMS :Ce ³⁺) yellow emitting phosphors are prepared by a solid-state reaction. Controllable luminescent intensity and emitting colour are studied as a function of Lu and Mg contents. Fixing the Mg content to be 1, the effect of Lu content on crystal phase formation, luminescence properties and temperature characteristics is studied. It is revealed that the Lu-induced luminescent enhancement is the result of an increase in absorbance of Ce³⁺ rather than the internal quantum efficiency. Intense and broadband emission is realized by controlling the Lu content to obtain a pure CLSMS crystal phase. The maximum luminescence intensity is obtained at x = 0.54, which is as high as 156% of the Lu-free phosphor. The Lu-containing phosphor also exhibits better temperature characteristics for its big activation energy (0.20 eV) than the Lu-free one (0.18 eV). Combining the present phosphor with a blue light-emitting diode (LED) chip, a white LED with an excellent colour rendering index R _a of 86 and a high luminous efficiency of 86 lmW^-1 is obtained. The results of the present study demonstrate that the CLSMS :Ce ³⁺ phosphors show a good performance and are attractive candidates for commercial applications when used in white LEDs.