Structural modulation induced intensity enhancement of full color spectra: a case of Ba3ZnTa2−xNbxO9:Eu3+ phosphors†
Modulation of structural order–disorder transition and structural oxygen defects can provide fundamental insights in the optimization of luminescence performances of phosphors. In this study, the luminescence of Ba3ZnTa2O9 (BZT) was systematically elucidated, including the emission arising from the charge transfer (Nb5+/Ta5+ → O2−) and anti-site oxygen defect emission due to the B-site disordering (defect type: [2ZnNb3− + 3Vo2+]), as corroborated by the electronic structural calculations and detailed experiments. We present a two-step design for the optimization of luminescence properties of Ba3ZnTa2O9 phosphor. In the first step, the B-site equivalent doping (Ta5+ substituted by Nb5+) was used to modulate the B-site atomic arrangement, which induced the formation of the cubic phase with B-site full disordering. In the second step, the A-site nonequivalent doping (Ba2+ substituted by Eu3+) was used to decrease the oxygen defect concentration. After the two-step optimization, the photoluminescence excitation spectrum of Ba3−yEuyZnNb2O9 (y = 0.1) shows a broad band excitation (300–400 nm), which is a good match with the near-UV LED chip emission. Even more importantly, the emission spectrum covers the entire visible spectral region and exhibits a remarkably enhanced emission intensity (a 40 times enhancement when compared to that of the intrinsic BZT). The fabricated LED device comprising an n-UV chip (λ = 370 nm) and a single-component Ba3−yEuyZnNb2O9 (y = 0.1) phosphor coating emits a warm white light with a low correlated color temperature (CCT = 4813 K) and a good color rendering index (Ra = 82.36).
- This article is part of the themed collection: Journal of Materials Chemistry C HOT Papers