Controlling of Structural Ordering and Rigidity of β-SiAlON:Eu through Chemical Cosubstitution to Approach Narrow-Band-Emission for Light-Emitting Diodes Application

Abstract

Narrow-band green-emitting phosphor β-SiAlON:Eu has been widely used in advanced wide-gamut backlighting devices. However, the origins for unusual sharp lines in photoluminescence emission at room temperature and tunable narrow-bandemission tailored by reducing Al-O in β-SiAlON:Eu are still unclear. Here, the presence of sharp-line fine structure in the emission spectra of β-SiAlON:Eu is mainly due to purely electronic transitions (zero phonon lines) and their vibronic repetitions resulted from the multi-microenvironment around Eu 2+ ions that has been revealed by relative emission intensity of sharp line depends on excitation wavelength and monotonously increasing decay time. The specific features of the Eu 2+ occupying interstitial sites indicate that the effect of crystal field strength can be neglected. Therefore the enhanced rigidity and higher ordering structure of β-SiAlON:Eu with decreasing the substitution of Si-N by Al-O become the main factors in decreasing electron-lattice coupling and reducing inhomogeneous broadening, favouring the blue-shift and narrow of the emission band, the enhanced thermal stability, as well as the charge state of Eu 2+ . Our results provide new insights for explaining the reason for narrow-band-emission in β-SiAlON:Eu, which will deliver an impetus for the exploration of phosphors with narrow band and ordering structure.

Ultra‐narrow band blue emission of Eu2+ in halogenated (Alumino)borate systems based on high lattice symmetry

“…For examples, some previous reports have a new perspective that the highly symmetric lattice structure could generate in a narrow fwhm. Zhang et al reported green emitting β‑SiAlON:Eu with narrow emission band (fwhm = 49 nm), which Eu 2+ ions occupy a highly rigid hexagonal channel. Braun et al reported layered‐structure M 3 Si 6 O 12 N 2 :Eu 2+ with highly pure green emission (fwhm = 65 nm).…”

New Insight for Luminescence Tuning Based on Interstitial sites Occupation of Eu2+ in Sr3Al2−xSixO5−xNxCl2 (x = 0–0.4)

“…Especially for x = 0 sample, it exhibits a serious thermal quenching, which attenuates more than 90% of RT emission intensity at 150 °C. We infer that the serious thermal quenching should be ascribed to the poor structure rigidity . Interestingly, the thermal stabilities have a continuous improvement with the increasing of Si 4+ N 3− substitution amounts.…”

Facile synthesis of the desired red phosphor Li2Ca2Mg2Si2N6:Eu2+ for high CRI white LEDs and plant growth LED device

“…Compared to SrLiAl 3 N 4 :Eu 2+ phosphor, Li 2 Ca 2 Mg 2 Si 2 N 6 :1.0%Eu 2+ gives a short wavelength emission at 638 nm, resulting in less part of emission outside the human eye sensitivity (green dotted line). Differencing from Eu 2+ ions in a highly symmetric cuboid like environment of SrLiAl 3 N 4 or in highly unusual EuN 9 coordination polyhedron of β‐SiAlON, this compound with distorted octahedral coordination for Eu 2+ still shows relative narrow band. The possible reason is that the lattice ions like Li, Mg, and Si occupy distinct lattice sites instead of the same lattice site with a statistical distribution, inducing small Stokes shifts and restricting inhomogeneous emission band broadening, thus narrow band occurs .…”

“…The PLE spectrum is obviously different from that at room temperature, which may be due to the phonon‐assisted transitions of zero phonon line. Under 460 nm excitation, Li 2 Ca 2 Mg 2 Si 2 N 6 :1.0%Eu 2+ phosphor exhibits the emission peak at 638 nm with FWHM of 62 nm. The powder gives a bright red light under 365 nm UV lamp irradiation (Figure A).…”

“…Mostly, the chemical shift of 29 Si is ranging from −40 to −60 ppm in nitrides. [19][20][21][22] There is only one sharp peak observed at −55 ppm, in line with one crystallographic Si site in the structure of Li 2 Ca 2 Mg 2 Si 2 N 6 . Considering the crystal structure of Li 2 Ca 2 Mg 2 Si 2 N 6 , the peak at −55 ppm could be assigned to the bow-tie units [Si 2 N 6 ] 10-, which also demonstrate that the purity of the sample and no Si-based impurity phase was generated.…”