Crystal structure, luminescence properties and thermal stability of BaY2−xEuxGe3O10 phosphors with high colour purity for blue-excited pc-LEDs

Abstract

A new series of BaY_2−xEu_xGe₃O₁₀ (x = 0.1–0.8) trigermanates has been synthesized using the solid-state reaction method. A powder XRD study has revealed that the compounds crystallize in the monoclinic system, space group P2₁/m, Z = 2. The crystal lattice consists of distorted Y/EuO₆ octahedra, trigermanate [Ge₃O₁₀]⁸⁻ groups and Ba atoms located in eight-fold coordinated irregular sites. Under UV and 465 nm light excitation, the samples exhibit reddish-orange emission corresponding to the characteristic ⁵D₀ → ⁷F_J transitions in Eu³⁺ ions. Concentration dependence study has shown that the powders with europium content x = 0.4–0.6 possess the highest luminescence intensity under 393 nm and 465 nm excitation. It has also been revealed that the predominant mechanism causing concentration quenching in the BaY_2−xEu_xGe₃O₁₀ series is due to multipolar interactions. The investigations on colour characteristics, quantum efficiency and thermal stability performance of BaY_2−xEu_xGe₃O₁₀ phosphors were carried out for the feasibility study of their practical application. The results indicate that BaY_2−xEu_xGe₃O₁₀ can be considered as a promising material for blue-excited phosphor-converted LEDs.