Structural Design of Cr<sup>3+</sup>-Activated Hexaaluminate Phosphors with High Quantum Efficiency and Cr<sup>3+</sup>–Cr<sup>3+</sup> Exchange Coupling Pairs
Hui Zhu, Chen Zhou, Siying Li, Huanhuan Chen, Xuan Shi, Yanyue Li, Pingzhi Zhang, Wei Li, Мaxim S. Моlokeev, Andrey Zolotov, Jing Wang, Zhi Zhou, Mao Xia
Abstract
Introducing large-radius cations usually causes structural relaxation, leading to a spectral redshift and low optical performance in Cr 3+ -activated phosphors. Here, MNAl 10 O 17:Cr 3+ phosphors are synthesized, and the substitution of large-radius cations induces the abnormal lattice shrinkage of the N site and atomic site splitting of the M site due to the unique hexaaluminate structure, further distinctly improving luminescent properties. To investigate the university of atomic site splitting, a series of phosphors, Na 2(1– m ) K 2 m Al 10.8 O 17:0.2Cr 3+ and Gd 1– n La n MgAl 10.8 O 19:0.2Cr 3+, are synthesized, and the variation of their luminescent properties conforms to the expected rule. Finally, Ga 3+ ions are introduced to improve the luminescence efficiency. Internal/external quantum efficiencies of the optimal sample are 98.1 and 65.8%, respectively. Meanwhile, an anomalous spectral blueshift indicates the existence of Cr 3+ –Cr 3+ exchange coupling pairs, and a comparative analysis of similar cases is conducted to provide some insights into the luminescence of coupling pairs.