S.C. Gedam

Photoluminescence of Dy3+ activator sensitized by Ce3+ in KNaSO4 microphosphor.

The KNaSO4 microphosphor doped with Ce or Ce and Dy prepared by a wet chemical method was studied by scanning electron microscopy (SEM) and characterized by photoluminescence (PL). KNaSO4 has a 5-µm particle size detected by SEM. The KNaSO4:Ce(3+) spectrum shows a single emission band at 327 nm for an excitation of 269 nm due to 5d → 4f transition of the Ce(3+) ion, indicating weak spin orbiting coupling of the Ce(3+) ground state. Efficient energy transfer takes place from Ce(3+) → Dy(3+) sublattices indicating that Ce(3+) could effectively sensitize Dy(3+) (orange emission) and that the Ce(3+) emission weakens significantly in KNaSO4. The powder form of prepared KNaSO4 show negligible change in morphologies and hence no effect on the particle size. The characteristics of this powder could provide improved luminescence properties. The development and understanding of this photoluminescence and the effect of Dy(3+) on KNaSO4:Ce(3+) are discussed.

Dy3+and Mn2+ emission in fluoride‐ and chloride‐based Na3(SO4)X (X = F or Cl) phosphors

In the present study, Na3 (SO4)X (X = F or Cl) halosulphate phosphors have been synthesized by the solid-state diffusion method. The phase formation of the compounds Na3 (SO4)F and Na3 (SO4)Cl were confirmed by X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na3 (SO4)F:Ce3+ and Na3 (SO4)Cl:Ce3+ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light and presents a dominant luminescence band centred at 341 nm for Ce3+, which is responsible for energy transfer to Dy3+ and Mn2+ ions. The efficient Ce3+  → Dy3+ energy transfer in Na3 (SO4)F and Na3 (SO4)Cl under UV wavelength was observed due to 4 F(9/2) to 6H(15/2) and 6H(13/2) level, while Ce3+ → Mn2+ was observed due to (4)  T1 state to (6) A1 . The purpose of the present study is to develop and understanding the photoluminescence properties of Ce3+ -, Dy3+ - and Mn2+ -doped fluoride and chloride Na3 (SO4)X (X = F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc.

Thermoluminescence properties of γ-irradiated KCaSO4Cl: X (X = Ce, Dy, Mn or Pb)

A new phosphor KCaSO4Cl is very interesting for thermoluminescent properties. In this article, we present results concerning the main dosimetric properties of KCaSO4Cl activated by Ce, Dy, Mn, and Pb at various concentrations. Polycrystalline KCaSO4Cl: (Ce; Dy; Ce, Dy; Mn; Ce, Mn; Pb and Ce, Pb) phosphors prepared by solid state diffusion method have been studied for its thermoluminescence (TL) characteristics. The TL glow curves of γ-irradiated all KCaSO4Cl samples show strong single glow peaks indicating that only one type of trap can be formed. The intensity of the TL glow peaks increases with increase of the γ-ray dose to the samples but the intensity of the TL glow peaks increases with decrease of the concentration of the dopent. The sensitivity of all the phosphors presented here are more than that of CaSO4: Dy. The phosphors have a simple TL glow curve structure with a prominent peak at the lower temperature side. TL response, fading, reusability of the phosphors are also studied, and it is found that the phosphor is quite suitable for use in dosimetry of ionizing radiations.

Photoluminescence enhancement in Na3SO4Cl:X (X = Ce3+, Eu3+ or Dy3+) material

The compound Na3SO4Cl X (X = Ce(3+), Eu(3+) or Dy(3+)) prepared by the wet chemical method was studied for its photoluminescence (PL) and energy transfer characteristics. The PL from Na3 SO4 Cl:Ce(3+) shows strong emission at 322 nm at an excitation of 272 nm. Therefore, an efficient Ce(3+) → Dy(3+), Eu(2+) → Dy(3+) and Eu(2+) → Eu(3+) energy transfer had taken place in this host. The Dy(3+) emission caused by Ce(3+) → Dy(3+) energy transfer under ultraviolet (UV) wavelengths peaked at around 477 nm and 572 nm due to (4) F9/2 → (6) H15/2 and (6) H13/2 transitions with yellow-orange emission in the Na3 SO4 Cl lattice. An intense Dy(3+) emission was observed at 482 and 576 nm caused by the Eu(2+) → Dy(3+) energy transfer process and due to (4) F9/2 → (6) H15/2 and (4) F9/2 → (6) H13/2 transitions respectively. The Eu(3+) blue to red light emission caused by the Eu(2+) → Eu(3+) energy transfer peaked at 593 nm and 617 nm due to (5) D0 → (5) D3 transitions. The presence of trivalent Eu in Na3 SO4 Cl suggested the presence of Eu(3+) in the host compound that occupied two different lattice sites and that peaked at 593 and 617 nm due to (5) D0 → (7) F1 and (5) D0 → (7) F2 transitions respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems due to its non-degenerate emitting (5) D0 state. The present paper discusses the photoluminescence characteristics of Eu(2+) → Dy(3+) and Eu(2+) → Eu(3+) energy transfer. This compound may be useful as a lamp phosphor.

Energy transfer between Ce3+ Gd3+ or Tb3+ in KNaSO4 microphosphor

KNaSO4 microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO4 has a 5-µm particle size detected by SEM. KNaSO4:Ce(3+),Tb(3+) showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb(3+) due to (5)D(4)  → (7)F(J) (J = 4, 5, 6) transitions. KNaSO4:Ce(3+),Gd(3+) showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce(3+)  → Gd(3+) and Ce(3+)  → Tb(3+) sublattices indicating that Ce(3+) could effectively sensitize Gd(3+) or Tb(3+) (green emission). Ce(3+) emission weakened and Gd(3+) or Tb(3+) enhanced the emission significantly in KNaSO4. This paper discusses the development and understanding of photoluminescence and the effect of Tb(3+) and Gd(3+) on KNaSO4:Ce(3+).

Study of luminescence and effect of Dy3+ on NaMgSO4Cl:Ce chlorosulphate phosphor

Chlorosulphate NaMgSO4 Cl phosphor doped with Ce(3+) and co-doped by Dy(3+) prepared by the wet chemical method was studied for its photoluminescence and thermoluminescence (TL) characteristics. The emission spectrum of Ce(3+) shows dominant peaks at 346 nm (excitation 270 nm) due to 5d → 4f transition. Efficient energy transfer occurs from Ce(3+) → Dy(3+) ions. Dy(3+) emission at 485 nm and 576 nm is due to (4)  F9/2 → (6) H15/2 and (4)  F9/2 → (6) H13/2 transitions of Dy(3+) ion respectively. The TL glow curves of NaMgSO4 Cl:Ce and Ce,Dy have been recorded for various concentrations at a heating rate of 2 °C/s irradiated by γ-rays at a dose rate of 0.995 kGy/h for 1 Gy, which peaks at about 241 °C and 247-312 °C respectively. Further, in changing the concentration level, the general structure of the intensity is found to increase. The main property of this phosphor is its sensitivity even for low concentrations of rare earth ions and low γ-ray dose. There is still scope for higher doses of γ-radiation. The phosphor presented may be used as a lamp phosphor as well as for TL studies.

Effect of γ-radiation on thermoluminescence in rare earths doped NaMgSO4Cl material

The thermoluminescence (TL) characteristics, effect of γ-radiation on NaMgSO4Cl: X (X = Tb; Ce, Tb; Dy; Dy, Eu) and trapping parameters in TL material prepared by wet chemical synthesis (WCS) method are studied. The intensity of these phosphors is compared with TLD CaSO4: Dy phosphor. The phosphor has a simple TL glow curve structure. The phosphors NaMgSO4Cl: Tb (between the range of 257–284°C); NaMgSO4Cl: Dy (173°C) and NaMgSO4Cl: Dy, Eu (156°C) have a single prominent peak, whereas NaMgSO4Cl: Ce, Tb has two peaks located at 154°C and 233°C indicating single and double trapping sites, respectively. It is found that intensity tends to be increase with increased concentrations of the activators. The TL glow curves of the phosphors have been recorded and irradiated at a rate of 0.99 kGyh−1 for 5 Gy γ-rays dose. The paper also discusses the kinetic parameters evaluated by Chens half width method such as activation energy E (eV) and frequency factor S (s−1).

Luminescence and spectroscopic studies of halosulfate phosphors: a review.

This review discusses the photoluminescence (PL) characteristics of halosulfate phosphors developed by us. Halosulfate phosphors KCaSO4 Cl:X,Y (X = Eu or Ce; Y = Dy or Mn) and Na6 (SO4 )2 FCl (doped with Dy, Ce or Eu) were prepared using a solid-state diffusion method. The mechanism of energy transfer from Eu(2+) →Dy(3+) , Ce(3+) →Dy(3+) and Ce(3+) →Mn(2+) has also been studied. Dy(3+) emission in the host at 475 and 570 nm is observed due to (4) F9/2 →(6) H15/2 and (4) F9/2 →(6) H13/2 transition, whereas the PL emission spectra of Na6 (SO4 )2 FCl:Ce phosphor shows Ce(3+) emission at 322 nm due to 5d→4f transition of the Ce(3+) ion. The main property of KCaSO4 Cl is its very high sensitivity, particularly when doped by Dy, Mn or Pb activators. This review also discusses the PL characteristics of some new phosphors such as LiMgSO4 F, Na6 Pb4 (SO4 )6 Cl2 , Na21 Mg(SO4 )10 Cl3 and Na15 (SO4 )5 F4 Cl.

Luminescence in Sr4Al14O25:Ce3+ aluminate phosphor

Cerium-doped Sr4 Al14 O25 phosphor is prepared using a single-step combustion synthesis and its X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and thermoluminescence (TL) properties are characterized. XRD reveals the formation of the desired phase in the prepared sample. SEM micrographs of the prepared Sr4 Al14 O25 phosphor show that the particle size is 10 µm. The prepared Sr4 Al14 O25 , along with Sr4 Al14 O25 :Cex (x = 0.5-5 mol%) shows a PL emission peak at 314 nm under UV excitation of 262 nm wavelength due to 5d → 4f transition. The phosphor is suitable for higher concentrations of Ce ions. The TL glow peak reveals three clearly visible distinct peaks at temperatures around 130, 231 and 336ºC. The three peaks are separated by deconvolution and kinetic parameters calculated using Chens peak shape method. The calculation shows that the reaction follows second-order kinetics with activation energy (E) values of 0.52, 0.81 and 1.12 eV, and frequency factor (s) values of 5.58 × 10(5) , 4.53 × 10(7) and 4.57 × 10(8) s(-1) for the three individual peaks.

Luminescence characteristics of Na3Ca2(SO4)3F: Ce3+ fluoride material

A new Na3Ca2(SO4)3F: Ce(3+) phosphor synthesized by a solid state diffusion method is reported. The photoluminescence study showed a single high intensity emission peak at 307 nm wavelength when excited by UV light of wavelength 278 nm. An unresolved peak of comparatively less intensity was also observed at 357 nm along with the main peak. The characteristic emission of dopant Ce in Na3Ca2(SO4)3F phosphor clearly indicated that it resides in the host lattice in trivalent form. The emission peak can be attributed to 5d → 4f transition of rare earth Ce(3+) . The prepared sample is also characterized for its thermoluminescence properties. The TL glow curve of prepared sample showed a single broad peak at 147°C. The trapping parameters are also evaluated by Chens method. The values of trap depth (E) and frequency factor (s) were found to be 0.64 ± 0.002 eV and 1.43 × 10(7)  s(-1) respectively. The study of PL and TL along with evaluation of trapping parameters has been undertaken and discussed for the first time.