Structural modulation induced intensity enhancement of full color spectra: a case of BaZnTaNbO:Eu phosphors

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 8; no. 2; pp. 6715 - 6723
• Main Authors: Li, Xiaohui, Zhou, Lei, Hong, Junyu, He, Shiman, Jing, Xiping, Drami anin, Miroslav D, Shi, Jianxin, Wu, Mingmei
• Format: Journal Article
• Language: English
• Published: 28.05.2020
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc01201g

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 Ba 3 ZnTa 2 O 9 (BZT) was systematically elucidated, including the emission arising from the charge transfer (Nb 5+ /Ta 5+ → O 2− ) and anti-site oxygen defect emission due to the B-site disordering (defect type: [2Zn Nb 3− + 3V o 2+ ]), as corroborated by the electronic structural calculations and detailed experiments. We present a two-step design for the optimization of luminescence properties of Ba 3 ZnTa 2 O 9 phosphor. In the first step, the B-site equivalent doping (Ta 5+ substituted by Nb 5+ ) 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 (Ba 2+ substituted by Eu 3+ ) was used to decrease the oxygen defect concentration. After the two-step optimization, the photoluminescence excitation spectrum of Ba 3− y Eu y ZnNb 2 O 9 ( 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 Ba 3− y Eu y ZnNb 2 O 9 ( 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 ( R a = 82.36). A single-component white phosphor Ba 2.9 Eu 0.1 ZnNb 2 O 9 with visible emission bands is realized by a two-step targeted structural modulation. Due to its remarkable properties, this phosphor may be used in solid state lighting devices.