Host composition dependent tunable multicolor emission in the single-phase Ba2(Ln1−zTbz)(BO3)2Cl:Eu phosphors

Abstract

A new strategy based on the host composition design has been adopted to obtain efficient color-tunable emission from Ba₂Ln_0.97−zTb_z(BO₃)₂Cl:0.03Eu (Ln = Y, Gd and Lu, z = 0–0.97) phosphors. This study reveals that the single-phase Ba₂Ln_1−zTb_z(BO₃)₂Cl compounds can be applied to use allowed Eu²⁺ absorption transitions to sensitize Eu³⁺ emission via the energy transfer Eu²⁺ → (Tb³⁺)_n → Eu³⁺. The powder X-ray diffraction (XRD) and Rietveld refinement analysis shows single-phase Ba₂Ln_1−zTb_z(BO₃)₂Cl. As-prepared Ba₂Ln_0.97−zTb_z(BO₃)₂Cl:0.03Eu phosphors show intense green, yellow, orange and red emission under 377 nm near ultraviolet (n-UV) excitation due to a variation in the relative intensities of the Eu²⁺, Tb³⁺ and Eu³⁺ emission depending on the Tb content (z) in the host composition, allowing color tuning. The variation in emission color is explained by energy transfer and has been investigated by photoluminescence and lifetime measurements and is further characterized by the Commission Internationale de l’éclairage (CIE) chromaticity indexes. The quantum efficiencies of the phosphors are high, up to 74%, and show good thermal stabilities up to 150 °C. This investigation demonstrates the possibility to sensitize Eu³⁺ line emission by Eu²⁺via energy migration over Tb³⁺ resulting in efficient color tunable phosphors which are promising for use in solid-state white light-emitting diodes (w-LEDs).