Synthesis and role of co-dopants (alkaline earth divalents and halides) on the photoluminescence of Eu2+ doped BaAl2O4 phosphor

Abstract

Pure and Eu 2+ doped BaAl2O4 phosphors have been synthesized by simple solid-state reaction technique. Synthesized BaAl2O4 samples were studied using powder X-ray diffraction analysis (XRD), Photoluminescence spectroscopy (PL), Fourier Transform -Infra Red Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). Alkaline earth divalent (Sr, Ca, Zn, Mg) and halides (F, Cl, Br, I) were used as co-dopants to enhance the PL properties of BaAl2O4:Eu 2+ phosphor. Significant impact of ionic radii of co-dopants on PL properties of the phosphor is reported.

Bluish-green afterglow and blue photoluminescence of undoped BaAl2O4

“…2(a), undoped BaAl 2 O 4 phosphors are prone to forming aggregates with irregular shapes. 4,7,12,14 The typical dimension of the aggregates is around 10 mm. Obviously, each aggregate is featured of a large number of pores which are distributed nonuniformly across the aggregate.…”

“…4 Irrespective of the difference in Re, the PL spectra of BaAl 2 O 4 :Eu 2+ ,Re 3+ are similar to that of Eu 2+ doped BaAl 2 O 4 (BaAl 2 O 4 :Eu 2+ ). 11–14 Consequently, Eu 2+ is generally assumed to be the luminescent center of afterglow and the luminescent center of PL for BaAl 2 O 4 :Eu 2+ and BaAl 2 O 4 :Eu 2+ ,Re 3+ . 1–18…”

“…11–14 Consequently, Eu 2+ is generally assumed to be the luminescent center of afterglow and the luminescent center of PL for BaAl 2 O 4 :Eu 2+ and BaAl 2 O 4 :Eu 2+ ,Re 3+ . 1–18…”

“…4 Irrespective of the difference in Re, the PL spectra of BaAl 2 O 4 :Eu 2+ ,Re 3+ are similar to that of Eu 2+ doped BaAl 2 O 4 (BaAl 2 O 4 :Eu 2+ ). [11][12][13][14] Consequently, Eu 2+ is generally assumed to be the luminescent center of aerglow and the luminescent center of PL for BaAl 2 O 4 :Eu 2+ and BaAl 2 O 4 :Eu 2+ ,Re 3+ . [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] This belief is, however, challenged by a number of theoretical and experimental results: (i) both undoped SrAl 2 O 4 and Eu 2+ doped SrAl 2 O 4 exhibit quite similar green aerglow; 19 (ii) both undoped CaAl 2 O 4 and Eu 2+ doped CaAl 2 O 4 exhibit quite similar blue aerglow; 20,21 (iii) the peak of the aerglow spectrum of Eu 2+ doped CaAl 2 O 4 does not shi regardless the variation in doping concentration; 22 (iv) the green aerglow of Dy 3+ doped SrAl 2 O 4 and Tb 3+ doped SrAl 2 O 4 is quite similar to the aerglow of Eu 2+ doped SrAl 2 O 4 ; [23][24][25][26] (v) Dy 3+ doped BaAl 2 O 4 exhibits bluish-green aerglow which is quite similar to that of BaAl 2 O 4 :Eu 2+ ; 7 (vi) density functional theory (DFT) calculations demonstrate that the aerglows of undoped SrAl 2 O 4 , undoped CaAl 2 O 4 and Eu 2+ doped SrAl 2 O 4 originate from oxygen vacancy and cation vacancy in the hosts; [19][20][21]27 (vii) oxygen vacancies are held responsible for the aerglows of a number of undoped inorganic materials such as HfO 2 , 28 SrAl 2 O 4 , 19...…”

“…Fig.2illustrates the morphology and microstructures of undoped BaAl 2 O 4 . As shown by the SEM micrograph in Fig.2(a), undoped BaAl 2 O 4 phosphors are prone to forming aggregates with irregular shapes 4,7,12,14. The typical dimension of the…”