New localized/delocalized emitting state of Eu2+ in orange-emitting hexagonal EuAl2O4

Abstract

Eu2+-activated phosphors are being widely used in illuminations and displays. Some of these phosphors feature an extremely broad and red-shifted Eu2+ emission band; however, convincing explanation of this phenomenon is lacking. Here we report a new localized/delocalized emitting state of Eu2+ ions in a new hexagonal EuAl2O4 phosphor whose Eu2+ luminescence exhibits a very large bandwidth and an extremely large Stokes shift. At 77 K, two luminescent sites responsible for 550 nm and 645 nm broadband emissions are recognized, while at room temperature only the 645 nm emission band emits. The 645 nm emission exhibits a typical radiative lifetime of 1.27 μs and an unusually large Stokes shift of 0.92 eV. We identify the 645 nm emission as originating from a new type of emitting state whose composition is predominantly that of localized 4f65d character but which also contains a complementary component with delocalized conduction-band-like character. This investigation provides new insights into a unique type of Eu2+ luminescence in solids whose emission exhibits both a very large bandwidth and an extremely large Stokes shift.

Substituting Different Cations in Tuning of the Photoluminescence in Ba3Ce(PO4)3

“…However, in the case of increased crystal-field splitting of Eu 2+ , there is something different between them, and we will talk about it in detail in the following. First of all, in the case of reabsorption, the emission with higher energy generally resonates with the lower-energy part of the excitation spectra, resulting in high-energy emission, which is partially reabsorbed, thus shifting the emission spectrum to the red region. , In this work, we can clearly see that PLE spectra shift to larger wavelength, as shown in Figure .…”

Redistribution of Activator Tuning of Photoluminescence by Isovalent and Aliovalent Cation Substitutions in Whitlockite Phosphors

“…27 For all this, we suppose that the saltatory variation is caused by Eu 2+ occupying different cation sites in the single phase phosphor. 28,29 For the no Sr sample, only one violet-blue emission band can be observed. However, when replacing Ca 2+ with Sr 2+ , extra emission bands appear successively.…”

New Insight into Phase Formation of MxMg2Al4+xSi5−xO18:Eu2+ Solid Solution Phosphors and Its Luminescence Properties

“…The PLE spectra of the M x Mg 2 Al 4+ x Si 5− x O 18 :0.03Eu 2+ (M = K, Rb) phosphors with optimal Eu 2+ content monitored at their strongest emission wavelength of 478 and 485 nm show characteristic excitation bands of Eu 2+ ion, which is broad in the range from 200 nm to 450 nm. Upon the excitation of 365 nm, the PL spectra of M x Mg 2 Al 4+ x Si 5− x O 18 :0.03Eu 2+ (M = K, Rb) exhibit blue emission bands, which are attributed to the 4f 6 5d-4f 7 transition of the Eu 2+ ion11. On the other hand, both the emission intensities and Full Width Half Maximum values (FWHM) were gradually enhanced as the M + concentration increases from x  = 0 to x  = 0.5 as shown in the inset of Fig.…”