Synthesis of the Red-Emitting (Ba, Ca)<sub>2</sub>ScAlO<sub>5</sub>:Eu<sup>3+</sup> Phosphors with Photoluminescence Properties
Yongfeng Cai, Yunfei Yang, Hexiong Liu, Ningning Song, Heng He, Jinshu Wang
Abstract
The light-emitting diodes (LED) are regarded as one of the most promising devices for inexpensive and widely used illumination; in particular, they are highly dependent on the development of red-emitting phosphors. Herein, we developed two types of red-emitting (Ba, Ca)2ScAlO5:Eu3+ multiple excitations phosphors (λex = 255–465 nm) via freeze-drying followed by calcination. Powder X-ray diffraction and NMR results point out that they have hexagonal space group P63/mmc (194), and the structural framework is composed of multi-coordinated Al3+–O2– polyhedron and Sc3+–O2– polyhedron. In addition, the valence state of europium (Eu3+) is confirmed by X-ray photoelectron spectroscopy characterization. Investigation on the photoluminescence properties showed that the photoluminescence process of (Ba, Ca)2ScAlO5:Eu3+ is attributable to the charge transfer band of Eu–O and abundant spectral terms of Eu3+. The α-(Ba, Ca)2ScAlO5:Eu3+ and β-(Ba, Ca)2ScAlO5:Eu3+ exhibited red emission under 465 and 395 nm excitation, respectively. The PL spectra and decay curves explain the intrinsic photoluminescence mechanism. The strongest emission peaks of the red-emitting α-(Ba, Ca)2ScAlO5:Eu3+ and β-(Ba, Ca)2ScAlO5:Eu3+ phosphors are at 615 and 619 nm, respectively, exhibiting a high fluorescence of 64 and 67% under the temperature of 423 K (150 °C). Further exploration of the red-emitting phosphors would provide a variety of choices for the design of red LEDs and white LEDs for the solid-state lighting system.