A novel single-phase color tunable LiYGeO4:Dy3+, Eu3+ phosphor exhibiting warm white light and excellent thermal stability

Abstract

LiYGeO₄ phosphors doped with Dy³⁺ and Eu³⁺ ions were synthesized using the solid phase method, and their color characteristics were adjustable. The bandgap value of LiYGeO₄ calculated by diffuse reflection data is very close to the theoretical value of 3.669 eV, indicating that LiYGeO₄ is an ideal candidate for doped rare earth activated ions. The analysis of the emission spectra and fluorescence attenuation curves of Dy³⁺ and Eu³⁺ co-doped LiYGeO₄ phosphors revealed a clear energy transfer process: energy transfer from Dy³⁺ to Eu³⁺. Analysis of emission spectra and fluorescence attenuation curves revealed a transfer of energy from Dy³⁺ to Eu³⁺. This transfer mechanism is attributed to the dipole–dipole interactions. In addition, by constantly adjusting the doping levels of Dy³⁺ and Eu³⁺, a warm white phosphor with a color temperature of 3881 K was obtained. Finally, the emission intensity of the LiYGeO₄:0.015Dy³⁺,0.02Eu³⁺ phosphor at 423 K was 86%, indicating that the phosphor has excellent thermal stability and 40% internal quantum efficiency, which proves the potential application of the LiYGeO₄ phosphor in white light-emitting diodes (w-LEDs).