Green Afterglow of Undoped SrAl2O4

Abstract

Undoped SrAl2O4 nanocrystals were obtained via solution combustion using urea as fuel. The afterglow properties of undoped SrAl2O4 were investigated. Green afterglow from undoped SrAl2O4 is visible to the human eye when the 325 nm irradiation of a helium–cadmium laser (13 mW) is ceased. The afterglow spectrum of undoped SrAl2O4 is peaked at about 520 nm. From the peak temperature (321 K) of the broad thermoluminescence glow curve, the trap depth of trap levels in undoped SrAl2O4 is estimated to be 0.642 eV using Urbach’s formula. Based on first-principles density functional calculations, the bandstructures and densities of states are derived for oxygen-deficient SrAl2O4 and strontium-deficient SrAl2O4, respectively. Our results demonstrate that the green afterglow of undoped SrAl2O4 originates from the midgap states introduced by oxygen and strontium vacancies. The observation of green afterglow from undoped SrAl2O4 helps in gaining new insight in exploring the afterglow mechanisms of SrAl2O4-based afterglow materials.

Photoluminescence and afterglow of Dy3+ doped CaAl2O4 derived via sol–gel combustion

“…This is the reason why some researchers indexed the peak at around 30.8° as (220). 7,8 Obviously, the diffraction peaks in Fig. 1 match well with the standard XRD diffractograms of monoclinic CaAl 2 O 4 .…”

“…Micrometer-sized pores are randomly distributed in the aggregates due to the production of a large amount of gases during the reaction. 3,8,[11][12][13]19,20 Fig. 2(b) shows the SEM micrographs of CaAl 2 O 4 :Dy 3+ to display the channels formed in the aggregates, each scale bar represents 2 mm.…”

Synthesis and effects of co‐dopants (La3+, Sm3+, Mn2+, Nd3+, V5+, Y3+) on photoluminescence of SrAl2O4:Dy3+ phosphor

“…Matsuzawa et al suggested that the band gap of this structure was about 6.52 eV [ 20 ] and considering this wide band gap, impurity‐free SrAl 2 O 4 crystal has no absorption ( λ excitation = 325 nm (3.8 eV), therefore, band‐to‐band emission is not possible in this crystal. [ 21 ] A different case was observed for undoped SrAl 2 O 4 , which is shown in Figure 6 that indicates certain defects are occurring in the host material during heat treatment and caused the emission band at 401 nm under the excitation of UV light (at 325 nm).…”

“…Matsuzawa et al suggested that the band gap of this structure was about 6.52 eV [20] and considering this wide band gap, impurity-free SrAl 2 O 4 crystal has no absorption (λ excitation = 325 nm (3.8 eV), therefore, band-to-band emission is not possible in this crystal. [21] A different case was observed for undoped SrAl 2 O 4 , which is…”

Sunlight activated ultra-stable long persistent luminescence glass ceramic for outdoor information display

“…This broad emission is ascribed to the existence of defects in the crystal structure because there is no activator in the glass and GC [26]. During the melt process with CO-rich reducing atmosphere, many oxygen vacancies are favorable to be formed in the glass system and preserved in the GC via in-situ precipitation [27], which lead to the generation of traps in the glass and crystal structures. The photoluminescence (PL) profile in the range of 14,285.74-33,333.33 cm −1 of the GC is asymmetric, which can be fitted into three emissions peaking at ~26,429.02 cm −1 (trap 1), ~22,123.89 cm −1 (trap 2), and ~19,685.04 cm −1 (trap 3) (Fig.…”