A red-emitting phosphor based on Eu3+-doped Li6SrLa2Ta2O12 garnets for solid state lighting applications

Abstract

The garnet-related Li6SrLa2−хEuxTa2O12 (x = 0.0–0.7) phosphors synthesized using a solid state method crystallize in the cubic space group Ia(Z = 8). These phosphors exhibit good thermal stability over a wide temperature range and an intense luminescence in the orange-red spectral region upon UV excitation. The Eu3+ ions occupy noncentrosymmetric sites with D2 symmetry in the Li6SrLa2Ta2O12 crystal structure, which leads to the predominance of the luminescence line associated with the forced electric dipole transition and provide high red color purity values. The Li6SrLa1.4Eu0.6Ta2O12 compound with 30 mol% europium concentration possesses the maximum light emission. The proximity of the CIE chromaticity coordinates of Li6SrLa2Ta2O12:Eu3+ compounds to the standard values for a red phosphor gives reason to consider europium-doped lithium tantalate with a cubic garnet structure as a promising material for the lighting application.