Crystal structure, luminescence properties and thermal stability of BaY_2-xEu_xGe₃O₁₀phosphors with high colour purity for blue-excited pc-LEDs

A new series of BaY2-xEuxGe3O10(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 groupP2(1)/m,Z= 2. The crystal lattice consists of distorted Y/EuO(6)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(5)D(0)->(7)F(J)transitions in Eu(3+)ions. Concentration dependence study has shown that the powders with europium contentx= 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-x)Eu(x)Ge(3)O(10)series is due to multipolar interactions. The investigations on colour characteristics, quantum efficiency and thermal stability performance of BaY(2-x)Eu(x)Ge(3)O(10)phosphors were carried out for the feasibility study of their practical application. The results indicate that BaY(2-x)Eu(x)Ge(3)O(10)can be considered as a promising material for blue-excited phosphor-converted LEDs.