White-light emission of Ca2La8(GeO4)6O2: Tb3+/Sm3+ nanocrystalline phosphors for solid-state lighting applications

Tb3+/Sm3+ ions co-doped Ca2La8(GeO4)6O2 (CLGO) phosphors are prepared by a pechini-type sol-gel technique. The nanocrystalline phosphors are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The photoluminescence emission and excitation spectra are measured for Tb3+, Sm3+ ions single-doped and Tb3+/Sm3+ ions co-doped phosphor samples individually. For the Tb3+/Sm3+ ions co-doped samples, we can observe emission covering the entire visible region with sharp peaks in the green, orange, and red regions. As the Sm3+ ion concentration increases, the Commission International de I'Eclairage chromaticity coordinates shift towards warm white-light region due to the energy transfer from Tb3+ to Sm3+ ions. This energy transfer property is clearly observable in the emission spectra under 374 nm excitation.