Engineering oxygen vacancies towards self-activated BaLuAl_xZn_4−xO_{7−(1−x)/2}photoluminescent materials: an experimental and theoretical analysis

Abstract

Novel self-activated yellow-emitting BaLuAl x Zn 4Àx O 7À(1Àx)/2 photoluminescent materials were investigated by a combined experimental and theoretical analysis. The effects of Al/Zn composition modulation, calcination atmosphere and temperature on the crystal structure and photoluminescence properties have been studied via engineering oxygen vacancies. Accordingly, BaLuAl 0.91 Zn 3.09 O 7 prepared in an air atmosphere was found to be the stable crystalline phase with optimal oxygen content and gave a broad yellow emission band with a maximum at 528 nm. The self-activated luminescence mechanism is ascribed to the O-vacancies based on the density functional theory (DFT) calculation. A theoretical model originating from the designed oxygen vacancies has been proposed in order to determine the influence of O-vacancies on the band structure and self-activated luminescence. Therefore, the appearance of a new local energy level in the band gap will cause the wide-band optical transitions in the studied BaLuAl x Zn 4Àx O 7À(1Àx)/2 materials.

Bright Red-Emitting Ca3LuAl3B4O15:Ce3+,Sm3+ Phosphors with High Thermal Stability for Elevating the Color Rendering of Near-Ultraviolet-Based White-Light-Emitting Diodes

“…The curve shape of CL 0.9 AB: x Sm 3+ was comparable to that of the host due to weak f–f transitions of Sm 3+ ions, while the bands in the range of 272–380 nm were observed for CL 0.9– x AB:0.1Ce 3+ , x Sm 3+ , ascribed to f–d absorptions of Ce 3+ ions. Generally, the band gap of the host material can be determined with the use of the following relation ,− where hv is the photon energy, A is the proportionality constant, and E g is the band gap. The values of n = 1/2 and n = 2 indicate the indirect and direct transitions respectively, and the F ( R ∞ ) value represents the Kubelka–Munk function, which is well-defined as where K , R , and S are the reflection, scattering coefficient, and absorption, respectively.…”

Incommensurately modulated structure and spectroscopic properties of CaGd2(MoO4)4:Ho3+/Yb3+ phosphors for up-conversion applications

“…Rare earth bearing oxide crystals are the basic luminescent materials in modern photonics and laser technology because of high emission efficiency, thermal and chemical stability, and different spectroscopic properties that can be tuned by composition [1][2][3][4][5][6][7][8][9]. One of the most interesting effects observed in rare-earth-doped photoluminescence materials is the frequency conversion from near infrared radiation of low photon energy to visible high photon energy radiation or upconversion (UC) [10][11][12][13][14][15][16][17][18][19][20].…”

Two-site occupancy induced the broad-band emission in the Ba4−x−ySryLa6O(SiO4)6:xEu2+ phosphor for white LEDs and anti-counterfeiting

“…Rare earth ion doped luminescent materials have been extensively studied in the fields of anti-counterfeiting, 1 lighting, 2 displays, 3 temperature sensing 4,26–28 and so on. 33–37 Due to the specific electronic structure of rare earth elements, the materials show rich luminescence color and intrinsic temperature dependence, etc . Among different rare earth ions, the Eu 2+ ion exhibits high efficiency, controllability and abundant luminescence characteristics, which have attracted more and more attention.…”