title: Crystal-site engineering control for the reduction of Eu(3+) to Eu(2+) in CaYAlO4: structure refinement and tunable emission properties.
abstract: In this article, Eu-activated CaYAlO4 aluminate phosphors were synthesized by a solid-state reaction. Under UV light excitation, characteristic red line emission of Eu(3+) was detected in the range of 570-650 nm. In addition, we introduced crystal-site engineering approach into the CaYAlO4 host through incorporation of Si(4+)-Ca(2+) to replace Al(3+)-Y(3+), which would shrink the AlO6 octahedrons, accompanied by the expansion of CaO9 polyhedron, and then enable the partial reduction of Eu(3+) to Eu(2+). The crystal structure and underlying mechanism have been clarified on the basis of the Rietveld refinement analysis. The PL spectra of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) exhibit both green emission of Eu(2+) (4f(6)5d(1)-4f(7), broadband around 503 nm) and red-orange emission of Eu(3+) ((5)D0-(7)F1,2, 593 and 624 nm) under UV light excitation with a quantum yield of 38.5%. The CIE coordinates of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) phosphors are regularly shifted from (0.482, 0.341) to (0.223, 0.457) with increasing x, which would expand the application of Eu. Furthermore, this investigation reveals the correlations of structure and property of luminescent materials, which would shed light on the development of novel phosphors suitable for lighting and display applications.
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xuejiao
authors.initials: X
authors.lastname: Li
authors.forename: Kai
authors.initials: K
authors.lastname: Li
authors.forename: Hongzhou
authors.initials: H
authors.lastname: Lian
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Shang
authors.forename: Jun
authors.initials: J
authors.lastname: Lin
keywords: Rietveld refinement; WLEDs; crystal-site engineering; phosphors; structure and property; tunable emission