Preparation of zero-thermal-quenching tunable emission bismuth-containing phosphors through the topochemical design of ligand configuration

Abstract

Bismuth-doped luminescent materials have obtained widespread attention for solid state lighting and optical sensing due to their excellent luminescence properties and preparation in a non-reducing green environment. However, the luminescence tuning of Bi³⁺ is a huge challenge, restricting its application. In this work, we regulate the emission of Bi³⁺ through the topochemical design of the ligand configuration and means of excitation-driven. When the ratio of Nb⁵⁺/Ta⁵⁺ in the host is changed, the dissymmetry in the lattice configuration of the two cations (Nb⁵⁺/Ta⁵⁺) makes the crystal electron cloud expand, and the nephelauxetic effect increases the bond length between the activator (Bi³⁺) and ligand (O²⁻) in the host, thereby reducing the field splitting energy of Bi³⁺, and the blue shift of Bi³⁺ emission is realized. When Bi³⁺ replaces Y³⁺, Bi³⁺ and O²⁻ form an irregular twisted octahedron, and each Bi³⁺ with a different lattice configuration is a luminescent site. The emission peak of Bi³⁺ can be red-shifted from 419 nm to 473 nm and is excitation-driven. On the basis of the tunable luminescence characteristics of the phosphor, a white-emitting single-phase phosphor (YNb_0.2Ta_0.8O₄:Bi³⁺,Eu³⁺) with adjustable corrected color temperature (CCT) was prepared by building Bi³⁺-Eu³⁺energy transfer. Even more surprising is that Eu³⁺ appears at zero thermal-quenching, and the emission intensity increases with increasing temperature. The emission intensity of Bi³⁺ can reach 62.3% at 423 K, and the phosphor can still emit warm-white light at a high temperature of 443 K. Furthermore, on the basis of the unique zero thermal quenching characteristics of Eu³⁺, a non-contact optical temperature sensing phosphor (YNb_0.8Ta_0.2O₄:Bi³⁺,Eu³⁺) was prepared. The material shows good temperature measurement performance in the temperature range of 303–523 K, and the relative sensitivity Sr reaches 1.80% K⁻¹. This topochemical design of ligand configuration provides a new perspective for the development of high-performance phosphors with tunable emission.