Non-concentration quenching, good thermal stability and high quantum efficiency of K5Y(P2O7)2:Eu3+/Tb3+ phosphors with a novel two-dimensional layer structure

Abstract

Developing new luminescent host materials has always been played a great promotion role in efforts to obtain high-efficiency and practical phosphors. In this work, three new diphosphates, K₅REE(P₂O₇)₂ (REE = Y, Eu, Tb), with basic isotype crystal structures were synthesized by a flux method. The structure consisted of two-dimensional (2D) [REE(P₂O₇)₂]_∞ anionic layers stacked along the b-axis. Within the structure of K₅Y(P₂O₇)₂ (KYP), interlayer Y³⁺ ions were about 5.6 Å away from each other, and intralayer Y³⁺ ions were separately larger than 9.5 Å, which were long enough to avoid concentration quenching in a high density of Eu³⁺/Tb³⁺ activators. Consequently, the absolute luminescent internal quantum efficiency (IQE) of the K₅Eu(P₂O₇)₂ and K₅Y_0.2Tb_0.8(P₂O₇)₂ phosphors were measured as high values of 81% and 80%, respectively. Moreover, the KYP:Eu/Tb phosphors showed good thermal stability at 30–200 °C, keeping more than 86% of the initial intensity at 200 °C. The achievement of this work is to provide a new host lattice template KYP for both Eu³⁺ and Tb³⁺ luminescence with a high IQE and good thermal stability.