A Color-tunable Nitride Phosphor for Near-Ultraviolet Excitation of White Light-emitting Diodes.

Due to the diversity of structure and composition and the unique coordination environment, nitride materials enable the doped activator ions to possess compelling luminescence characteristics, such as rich emission colors, favorable stability and tunable emission spectra. Here, novel SrLuSi4 N7 :Ce3+ ,Tb3+ nitride phosphors were successfully synthesized by a modified carbothermal reduction and nitridation method at atmospheric pressure. SrLuSi4 N7 (SLSN) belongs to hexagonal symmetry, with space group P63 mc, and its crystal structure is composed of the basic building block with corner-sharing [SiN4 ] tetrahedron. Under 365 nm excitation, SLSN:Ce3+ exhibits a broad emission band peaking at 450 nm with a full width at half-maximum (FWHM) of 92 nm and the most forceful intensity obtained at the Ce3+ concentration amount of 0.04. On the basis of the efficient energy transfer, SLSN:Ce3+ ,Tb3+ exhibits color-tunable emission from blue (450 nm) to green (545 nm). Our results indicate that SLSN nitride phosphor is a promising candidate for near-ultraviolet (n-UV) based white LEDs.

Structural Evolution and Effect of the Neighboring Cation on the Photoluminescence of Sr(LiAl3 )1-x (SiMg3 )x N4 :Eu2+ Phosphors.

In this study, a series of Sr(LiAl3 )1-x (SiMg3 )x N4 :Eu2+ (SLA-SSM) phosphors were synthesized by a solid-solution process. The emission peak maxima of SLA-SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. 7 Li solid-state NMR spectroscopy was utilized to distinguish between the Li(1)N4 and Li(2)N4 tetrahedra in SLA-SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature-dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X-ray absorption near-edge structure studies reveal that the Eu2+ concentration in SLA-SSM is much higher than that in in SrLiAl3 N4 :Eu2+ and SrSiMg3 N4 :Eu2+ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.

Substitutional disorder in Sr2-yEuyB2-2xSi2+3xAl2-xN8+x (x ≃ 0.12, y ≃ 0.10).

A novel nitride, Sr2-yEuyB2-2xSi2+3xAl2-xN8+x (x ≃ 0.12, y ≃ 0.10) (distrontium europium diboron disilicon dialuminium octanitride), with the space group P62c, was synthesized from Sr3N2, EuN, Si3N4, AlN and BN under nitrogen gas pressure. The structure consists of a host framework with Sr/Eu atoms accommodated in the cavities. The host framework is constructed by the linkage of MN4 tetrahedra (M = Si, Al) and BN3 triangles, and contains substitutional disorder described by the alternative occupation of B2 or Si2N on the (0, 0, z) axis. The B2:Si2N ratio contained in an entire crystal is about 9:1.