Optical Properties of NaCl:Sn²⁺Phosphor Synthesized from Aqueous NaCl/SnCl₂/HCl Solution

Abstract

A NaCl:Sn 2+ phosphor was synthesized from an aqueous NaCl/SnCl 2 /HCl solution. The optical properties of the as-synthesized phosphor material were investigated by diffuse reflectance spectroscopy, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and luminescence decay time measurement. The effects of temperature and excitation wavelength on the emission spectra were thoroughly studied in the present study. The temperature dependence of the PL spectra was examined between T = 20 and 300 K in 10 K increments, while the PLE spectra were obtained by excitation with λ ex ∼ 250-330 nm in the same temperature range. The PL spectra revealed four independent emission bands with peaks at ∼440 nm (B1), ∼490 nm (B2), ∼540 nm (G), and ∼635 nm (R). The B1 and G emission bands were assigned to the A T and A X emission bands typically observed in ns 2 -doped alkali halide phosphors, whereas the B2 and R emission bands were attributed to the Sn 2+ − V − Na (cation vacancy) dipole aggregates.Alkali halide phosphors that contain heavy-metal ions with an s 2 configuration have received a great deal of attention both from theoretical and experimental point of views. 1-8 A considerable number of studies have reported the photoluminescence (PL) properties of Sn 2+ -activated alkali halides (such as KCl:Sn 2+ , [9][10][11][12][13] KBr:Sn 2+ , 10,14-17 and KI:Sn 2+ , 14,18-29 ) and other phosphors. 30 However, complete studies on the PL properties of Sn 2+ -activated NaCl phosphors are scarce in the literature. [31][32][33] Kynev and Tabakova 31 studied the effects of divalent cation additives (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , and Cd 2+ ) on the PL and PL excitation (PLE) properties of NaCl:Sn 2+ phosphor. The addition of such divalent cations along with the Sn 2+ activator caused significant changes in both the PL and PLE properties of the phosphor. The divalent cations could be divided into two groups on the basis of the effects they produce. The first group of cations (Zn 2+ , Cd 2+ , and Mg 2+ ) produced new, shorter-wavelength emission bands located at ∼440-465 nm along with long-wavelength emission bands in the 520-530 nm region. Interestingly, the emission band at ∼490 nm, which is a characteristic of NaCl:Sn 2+ , was no longer present after addition of these cations. The second group of cations (Ca 2+ , Ba 2+ , and Sr 2+ ) caused a redshift in the ∼490 nm emission band together with an appreciable increase in its spectral width.Mȃrculescu et al. 32 investigated the PL and PLE properties of a Bridgman-grown NaCl:Sn 2+ phosphor with particular emphasis on the effects of concentration and thermal history of the crystals. The aggregation centers formed in NaCl:Sn 2+ showed absorption and emission bands different from those of isolated Sn 2+ − V − Na (cation vacancy) dipoles. PL properties of Sn 2+ -sensitized Mn 2+ centers in NaCl were also investigated by Muñoz F. and Rubio O. 33 Thermoluminescence (TL) emission and decay kinetics of Sn 2+ -doped NaCl were studied by Acharya et al. 34 They reported that th...

IR Emission Band and Multiple-Peak Structure in Photoluminescence Spectra of SnO2:Mn

“…8a) is in agreement with those observed in many Sn 2+ -activated phosphors. 20 The R emission peak observed here also corresponds to the A X emission band usually observed in Sn 2+ -activated alkali halides (e.g., NaCl, KCl, KI, and KBr) 19,21,22 and SnCl 2 (Ref. 18) (i.e., it may be due to defect levels associated with oxygen vacancies or Sn interstitials in SnO 2 ).…”

“…12a are mainly due to the excitation of Sn 2+ in the SnO 2 host, i.e., the absorption in the 4−5 eV region is due to the 1 S 0 → 3 P 1 (A 1 , A 2 ) and 1 S 0 → 3 P 2 (B) transitions and that above ∼5 eV is due to the 1 S 0 → 1 P 1 (C 1 −C 3 ) transition. [18][19][20] The dashed line in Fig. 12a represents the PLE spectrum of the Sn 2+related A T emission band observed in NaCl:Sn 2+ .…”

Excitation Energy Transfer from Ce3+to Sn2+in NaCl Phosphor

“…These emission bands are traditionally assigned to energy levels arising from the Jahn−Teller effect on the triplet state of s 2 ions in alkali halides (A T and A X ). 24 The PL and PLE spectra of NaCl:Ce 3+ , Sn 2+ in Fig. 8c are observed to be nearly the same as those for NaCl:Sn 2+ (Fig.…”

“…8b is characterized by the A ( 1 S 0 → 3 P 1 ), B ( 1 S 0 → 3 P 2 ), and C ( 1 S 0 → 1 P 1 ) absorption peaks, in the order of increasing photon energy. 24 These absorption peaks have Figure 9. Energy-level scheme for Sn 2+ and Ce 3+ ions representing the PL and PLE processes in (Ce 3+ , Sn 2+ )-codoped NaCl phosphor.…”

“…22 Previously, alkali halide phosphors contain heavy-metal ions with an s 2 configuration like Sn 2+ , Pb 2+ , and Tl + , received a great deal of attention both from theoretical and experimental point of views. 24 However, there has been no detailed studies on the codoping effects of Ce 3+ and Sn 2+ neither in NaCl nor in other host materials. Only a few authors reported results on the codoping effects of Ce 3+ and Sn 2+ in SrGa 2 S 4 (Ref.…”