A Red Long-Lasting Phosphorescence Material Gd_9.33(SiO₄)₆O₂:Sm³⁺and Effect of Oxygen Vacancies on Its Performance

Abstract

A novel red long-lasting phosphorescence material Gd9.33(SiO4)6O2:Sm3+ was reported in this paper. There are two kinds of Gd sites occupied by Sm3+ ions in this host matrix, Gd1 (CN = 9) and Gd2 (CN = 7). The Gd2 site is surrounded by six oxygen atoms bonded to silicon and one free oxygen atom which may be missed easily and then become an oxygen vacancy. A significant sequential enhancement on the afterglow performance of the air-sintered, the vacuum-sintered and the reduction-sintered samples was observed. This improvement could be attributed to the increase of oxygen vacancies acting as sensitizer and electron traps for afterglow, which was investigated with thermoluminescence. It is established that, the traps arising from oxygen defects (oxygen vacancies mostly) are responsible for the afterglow phenomenon of the Gd9.33(SiO4)6O2:Sm3+ phosphor.

Phosphorescence behavior and photoluminescence mechanism of Dy 3+ sensitized β-Zn 3 (PO 4 ) 2 : Mn 2+ phosphor

“…Moreover, the defects of oxygen vacancies usually appear in the oxide host when a sample is sintered at reducing atmosphere [43]. It was reported that the increase of the Sm 3+ ion doping concentration in Gd 9.33 (SiO 4 ) 6 O 2 : Sm 3+ phosphors resulted in the stable enhancement of the TL peak at 343 K, indicating that quantity of traps increased gradually and also perfected the luminous properties [36]. As shown in Fig.…”

“…In the reports [27,36,42], the TL peak at 343 K in both bZn 3 (PO 4 ) 2 : Mn 2+ and Gd 9.33 (SiO 4 ) 6 O 2 : Sm 3+ and the TL peak at 325 K in Sr 2 SnO 4 : Sm 3+ were all attributed to the defects of oxygen vacancies. Moreover, the defects of oxygen vacancies usually appear in the oxide host when a sample is sintered at reducing atmosphere [43].…”

“…It has been shown that too much dopant of Dy 3+ ions resulted in decreased luminescent properties of SrAl 2 O 3 : Eu 2+ , Dy 3+ phosphors, an effect attributed to the concentration quenching [33]. In addition, the probability of non-radiative energy transfer from one ion to another increases as the distance between vicinal ions decreases due to the increase of ion doping concentration [34][35][36]. In this experiment, it was observed that the LPP performance of b-Zn 3 (PO 4 ) 2 : Mn 2+ phosphors was steadily improved with the increase of Dy 3+ and then declined with the continuous increase of Dy 3+ at more than 2.0 mol%.…”

Luminescent and magnetic properties of the afterglow phosphors GdSr2AlO5:RE3+ (RE3+ = Eu3+, Sm3+, Pr3+ and Dy3+)

“…The electric-dipole transition ( 5 D 0 -7 F 2 ) is stronger than the magnetic-dipole transition ( 5 D 0 -7 F 1 ), indicating that Eu 3+ ions occupy a low-symmetry site. 25,26 In GdSr 2 AlO 5 :Eu 3+ , the 5 D 0 -7 F 4 transition at 703 nm is the strongest, which is greatly appropriate for applications in biomedical imaging. 13 Generally, dominant 5 D 0 -7 F 4 transitions are not oen found in the PL spectra of Eu 3+ ions.…”

“…43) and Gd 9.33 (SiO 4 ) 6 O 2 :Sm 3+ . 25 It is well known that the oxygen vacancies, which act as electron traps, play major roles in the aerglow time in LLP materials. 43 In the TL curve, the intensity corresponds to the quantity of traps.…”