S.K. Omanwar

Combustion synthesis and preliminary luminescence studies of LiBaPO4 : Tb3+ phosphor

The polycrystalline sample of LiBaPO4 : Tb3+ (LBPT) was successfully synthesized by solution combustion synthesis and studied for its luminescence characteristics. The thermoluminescence (TL) glow curve of LBPT material consists of two peaks at 204.54 and 251.21°C. The optimum concentration was 0.005 mol to obtain the higher TL intensity compared to commercial TLD-100 phosphor. The peak shape method was used to calculate kinetic parameter (activation energy and frequency factor). In CW-OSL mode its sensitivity for beta exposure was found to be 50% compared to commercially available α-Al2O3 : C and 40% than LMP (BARC), and photoluminescence spectrum of LBPT shows green emission when excited with 225 nm UV source.

Aldo-keto synthesis effect on Eu3＋fluorescence in YBO3 compared with solid state diffusion

Abstract The red-orange emitting phosphor YBO 3 :Eu 3+ was prepared by aldo-keto method and solid state diffusion. Aldo-keto method implied to decrease the processing time and heating temperature. The red-orange emitting phosphor was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as emission and excitation photoluminescence spectra recorded at room temperature. The result of aldo-keto method showed that the phosphor YBO 3 :Eu 3+ could be obtained at 900 °C in less time ∼60% as compared to solid state diffusion (SSD). The material showed that the strongest emission peak at 595 nm under excitation at 233 nm was only due to forced magnetic dipole 5 D 0 → 7 F 1 transition of Eu 3+ ions. Significantly, the emission intensity of YBO 3 :Eu 3+ phosphor prepared by aldo-keto method was relatively higher as compared to that obtained by the solid state diffusion.

A Potential Candidate for Lamp Phosphor: Eu3

The novel phosphor K2Y2B2O7 doped with europium is studied for its photoluminescence properties. The studies show that the phosphor gives strong red emission (PL) at 613 nm related to 5D0-7F2 transition of Eu3

Synthesis and photoluminescence study of narrow-band UVB-emitting LiSr4(BO3)3:Gd3+, Pr3+ phosphor

A series of Pr3+, Gd3+ and Pr3+–Gd3+-doped inorganic borate phosphors LiSr4(BO3)3 were successfully synthesized by a modified solid-state diffusion method. The crystal structures and the phase purities of samples were characterized by powder X-ray diffraction. Surface morphology of the sample was studied by scanning electronic microscopy (SEM). The optimal concentrations of dopant Gd3+ ions in compound LiSr4(BO3)3 were determined through the measurements of photoluminescence (PL) spectra of phosphors. Gd3+-doped phosphors LiSr4(BO3)3 show strong band absorption in UV spectral region and narrow-band UVB emission under the excitation of 276 nm was only due to 6PJ → 8S7/2 transition of Gd3+ ions. The effect of Pr3+ ion on excitation of LiSr4(BO3)3:Gd3+ was also studied. The excitation of LiSr4(BO3)3:Gd3+, Pr3+ gives a broad-band spectra, which show very good overlap with the Hg 253.7 nm line. The photoluminescence spectra of LiSr4(BO3)3 with different doping concentrations Pr3+ and keeping the concentration of Gd3+ constant at 0.03 mol have also been studied. The emission intensity of LiSr4(BO3)3:Pr3+–Gd3+ phosphors increases with increasing Pr3+ doping concentration and reaches a maximum at 0.01 mol. From the photoluminescence study of LiSr4(BO3)3:Gd3+, Pr3+ we conclude that there was efficient energy transfer from Pr3+→ Gd3+ ions in LiSr4−x−yPrxGdy(BO3)3 phosphors.

Synthesis and effect of partially replacement of Y 3+ to La 3+ -ions on their photoluminescence properties of (Y (1− x ) La x )PO 4 :Eu 3+ phosphor

A series of Eu3+-doped (Y(1−x)Lax)PO4 phosphors were synthesized using a slow evaporation method increasing molar ratios of La3+ ions in (Y(1−x)Lax)PO4:0.01Eu3+. The crystal structure and photoluminescence (PL) with decay curves of the samples were characterized using X-ray diffraction (XRD) and fluorescence spectroscopy, respectively The PL intensity is higher for the monoclinic than tetragonal structure of the (Y(1−x)Lax)PO4:Eu3+ phosphor. The CIE color coordinates shows that the color purity increases, when the La3+ ions are completely replaced by Y3+ ions.

Synthesis and luminescent properties of Tb3+-activated novel magnesium alumino-borate phosphor

A new green phosphor, MgAl2(1–x)B2O7:xTb3+ (x = 0.005, 0.01, 0.02 and 0.03 mole) has been synthesized by a solution combustion synthesis method. The crystal phase and surface morphology of the prepared phosphor have been studied by the powder X-ray diffraction and the field emission-scanning electron microscopy images, respectively. The excitation and emission spectra indicate that this phosphor can be effectively excited by the ultraviolet 234 nm, and exhibit bright green emission centered at 544 nm corresponding to the 5D4→7F5 transition along with 490 nm (5D4→7F6), 585 nm (5D4→7F4) and 622 nm (5D4→7F3) of Tb3+ ions. It is shown that the 3 mol% of doping concentration of Tb3+ ions in MgAl2B2O7:Tb3+ phosphor is optimum, and the concentration quenching occurs when the Tb3+ concentration is beyond 2 mol%. The concentration quenching mechanism can be interpreted by the exchange interaction of Tb3+ ions. This work suggests that the novel green phosphor is a kind of potential green-emitting phosphor.

Synthesis and luminescence properties of Tb3+-doped LiMgPO4 phosphor

Polycrystalline sample LiMg(1−x)PO4:xTb3+ (x = 0.001, 0.002, 0.005, 0.01, 0.02) phosphor was synthesized via modified solid state method (MSSM). The prepared sample was characterized through XRD pattern (X-ray diffraction) and SEM (scanning electron microscope). Additionally, photoluminescence (PL), optically stimulated luminescence (OSL), thermoluminescence (TL) and other dosimetric properties including dose linearity, reusability and fading were studied. In OSL mode, sensitivity of prepared phosphor was found to be 2.7 times that of LiMgPO4:Tb3+, B (BARC) phosphor and 4.3 times that of α-Al2O3:C (BARC) phosphor. The TL glow consists of overlapping peaks in temperature range of 50–400∘C and first peak (P1) was observed at 150∘C, second peak (P2) at 238∘C, third peak (P3) at 291∘C and fourth peak (P4) at 356∘C. The TL sensitivity of second peak (P2) of LiMgPO4:Tb3+ phosphor was compared with α-Al2O3:C (BARC) phosphor and found to be 100 times that of the α-Al2O3:C (BARC) phosphor. The minimum detectable dose (MDD) was found to be 5.6 μGy. Moreover, photoionization cross-sections, linearity, reusability, fading and kinetic parameters were calculated. Also, photoluminescence spectra of LiMgPO4: Tb3+ shows characteristic green–yellow emission exciting at 224 nm UV source.

Near-infrared spectral downshifting in Sr(3−x)(VO4)2:xNd3+ phosphor

In this study, the spectral downshifting (DS) from ultraviolet (UV) light to near-infrared (NIR) radiation in Sr3(VO4)2:Nd3+ phosphor is reported. The prepared materials were characterized by X-ray powder diffraction (XRD) and photoluminescence (PL) properties along with steady state luminescence time decay curves were studied, which confirmed the energy transfer (ET) from VO43−

Effect of calcination temperature on structural and optical properties of europium (III) doped SrO–Y2O3 phosphor

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Exploring Synthesis Techniques for Yttrium Based Phosphors

ions to Nd3+ ions. The DS phenomenon by phosphor was observed, which involved emission of NIR photons (1075 and 1064 nm) and visible photons (506 nm) from absorbed UV photons at 349 nm. The theoretical energy transfer efficiency (ETE) was calculated with the help of steady state luminescence time decay curves and the maximum ET efficiency approached up to 41.33%. The crystalline silicon (c-Si) cell has maximum efficiency in NIR region of solar spectrum due to an energy band gap of 1.12 eV. Sr3(VO4)2:Nd3+ can be potentially used as a NIR DC phosphor for c-Si solar cells.