Olivine-type germanate phosphors doped with Ln3+ (Ln = Eu, Dy) for solid-state lighting

Abstract

Olivine-type germanate ceramics doped with Ln³⁺ ions (where Ln = Eu, Dy) as potential candidates to generate visible luminescence were studied. Analysis of microstructure and phase identification in systems obtained using the solid-state reaction method indicate that ceramics Li₂ZnGeO₄ and Li₂MgGeO₄ crystallize in a monoclinic crystal lattice, and samples consist of agglomerates that differ in size and shape. The spectroscopic properties of the ceramics align with the structure, and crucial parameters like the R/O or Y/B ratio and luminescence lifetime strongly depend on the type of ceramic samples. The luminescence spectra for germanate ceramics were recorded depending on the excitation wavelength and analyzed in detail. The Commission Internationale de l’Éclairage (CIE) chromaticity coordinates (x, y) were calculated from the emission spectra. It was observed that the color parameters change when the excitation wavelength and composition are modified. Our results indicate that olivine-type germanate ceramics doped with Eu³⁺ and Dy³⁺ ions exhibit red-orange and yellow-white emissions, respectively.