Dependence of Luminous Performance on Eu3+ Site Occupation in SrIn2(P2O7)2: The Effect of the Local Environment

The photoluminescence behavior of luminescent materials with rare earth (RE) ions as a luminescence center not only depends on the element type and chemical valence of RE ions but also on their concentration and occupation in the matrix, sometimes including the interaction of the matrix and RE ions or between different RE ions. Herein, special SrIn2(P2O7)2 phosphate, assembled by monolayer [SrO10]∞ and bilayer [In2P4O14]∞ consisting of InO6 units and P2O7 groups, was selected as the host material, and different cation positions (Sr and In) were substituted by Eu3+. The structure refinement in combination with Judd-Ofelt theory has shed light on the differences of the Eu3+ coordination environment in SrIn2(P2O7)2. The structural rigidity of the In3+ site is better than that of the Sr2+ site, making SrIn1.92(P2O7)2: Eu0.08 superior in thermal stability. The average distance between adjacent Sr2+ ions is larger than that between adjacent In3+ ions, causing the higher quantum efficiency of Sr0.9In2(P2O7)2: Eu0.1. The present work demonstrates that the site occupation of Eu3+ has an important effect on its luminous performance. Importantly, the newly developed Eu3+-doped SrIn2(P2O7)2 phosphors, exhibiting outstanding luminous efficiency, favorable thermal stability, and excellent color purity, are promising red components of phosphor-based light-emitting diodes.