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Gadolinium (Gd3+) ion-activated SrY2O4 phosphors with varying concentrations of Gd3+ ions were prepared using sol–gel synthesis. The photoluminescence spectra were recorded to study the luminescence behavior of the as-synthesized phosphors. Upon excitation at 275 nm, the material displayed two bands, one at 309 nm (6P5/2 → 8S7/2) and the other at 315 nm (6P7/2 → 8S7/2), in the narrowband ultraviolet (UV) spectral regions. The strong emission at 315 nm indicated that the phosphors could be used as a narrowband UV light source. Electron paramagnetic resonance spectra showed a foremost Gd3+ center with weak signals. Several resonance signals revealed that Gd3+ ions underwent different Zeeman interactions and exhibited varying crystal field strength. The results suggest the potential utility of Gd3+ doped-SrY2O4 phosphors for phototherapy lamp applications which require UV emission. [ABSTRACT FROM AUTHOR]

Calcium aluminozincate phosphor, Ca 3 Al 4 ZnO 10 (CAZ) doped with Eu3+ has been synthesized using solid-state reaction (SSR), combustion (CS) and sol-gel (SG) methods for relatively improved luminescence performance and to optimize synthesis method. The X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and PL decay measurements have been recorded for the detailed investigation of the luminescence properties of the as-synthesized phosphor. The thermoluminescence (TL) spectral study has been done to estimate the trap depth of the defect centres. The XRD peaks confirm the complete matching of the diffraction peaks of the as-synthesized sample with the standard data for Ca 3 Al 4 ZnO 10. The morphology of the sample synthesized via SG method shows agglomerated particles with average particle size smaller than the samples synthesized via CS and SSR method. The detailed investigation shows significant red emission enhancement in Eu3+ doped CAZ phosphor synthesized via SG method. The obtained results suggest that the Eu3+ doped CAZ phosphor synthesized via SG method could be a great choice as red emitter for applications in solid state lighting. • Optimized synthesis technique for calcium aluminozincate (CAZ) phosphors. • Phase confirmation observed in solid-state, combustion and sol-gel method. • Enhancement in red emission under blue excitation for sol-gel synthesized phosphors. • CIE coordinates are close to commercial red phosphor. • Conducted thermoluminescence studies to identify trap centres in CAZ phosphors for the first time. [ABSTRACT FROM AUTHOR]

Trivalent gadolinium (Gd3+) activated CaY2Al4SiO12 garnet compounds with a variable concentration of Gd3+ ions were synthesized by a sol–gel method. The synthesized garnet compounds were characterized for their structural, morphological, luminescent, and magnetic properties. The x-ray diffraction data of Gd3+ activated CaY2Al4SiO12 garnet compound reveal the cubic structure with Ia3d space group. The scanning electron microscope images represent the morphology of the particles. The photoluminescence properties were analyzed from the excitation and emission spectra. The emission spectra of the CaY2Al4SiO12:Gd3+ garnet compound under 273 nm excitation exhibit two emission peaks at (308 nm and 314 nm) nm and are attributed to 6P5/2 → 8S7/2 and 6P7/2 → 8S7/2 transitions, respectively. The emission peak observed at 314 nm is more intense than the peak observed at 308 nm. The high-intensity peak at 314 nm is used to cure various skin disorders, and hence is beneficial in phototherapy. The intensity of the emission peaks increases up to 0.09 mol of Gd3+ ion concentration in the CaY2Al4SiO12 garnet compound, and beyond, then decreases, showing concentration quenching. The electron paramagnetic resonance of Gd3+ ions in the prepared garnet compound exhibits resonance signals with effective g values at g ≈ 6.5, 5.0, 2.6, 2.2, 2.0, and 1.6 of the U-spectrum, due to cubic, octahedral, or tetrahedral distorted sites. [ABSTRACT FROM AUTHOR]

Trivalent europium ions (Eu 3+ ) doped calcium aluminozincate (CAZ) phosphors blended with various fluxes (NaF, NaCl and Na 2 B 4 O 7 ) have been synthesized by conventional solid-state reaction method. The structural, morphological and luminescent properties along with lifetimes have been investigated in detailed. The Judd-Ofelt (J-O) analysis has been carried out to get insight of optical properties. The X-ray diffraction (XRD) pattern confirms the single phase orthorhombic structure for Eu 3+ doped CAZ phosphor with NaCl and Na 2 B 4 O 7 fluxes; whereas the phase purity has not been achieved in NaF assisted Eu 3+ doped CAZ phosphor. The as-synthesized phosphor has uneven agglomerated micron sized particles. The photoluminescence (PL) studies exhibit significant enhancement in the red emission for Eu 3+ doped CAZ phosphor with the addition of Na 2 B 4 O 7 . The emission intensity has been found to increase approximately 1.5 times using NaCl and 2.5 times for Na 2 B 4 O 7 in Eu 3+ doped CAZ phosphor as compared to the phosphor without any flux. The emission spectrum of optimized Eu 3+ doped CAZ phosphor added with Na 2 B 4 O 7 flux has been compared with the commercial Y 2 O 3 : Eu 3+ phosphor. The CIE chromaticity coordinates and color purity calculated for Na 2 B 4 O 7 in Eu 3+ doped CAZ phosphor is close to commercial red phosphor. The decay curves show bi-exponential behaviour with experimental lifetimes in the range of microseconds for the as-prepared phosphors. All these results indicate that the Na 2 B 4 O 7 flux assisted Eu 3+ doped CAZ phosphor can serve as an efficient red phosphor under blue light for applications in white light emitting devices. [ABSTRACT FROM AUTHOR]

The Dy 3+ ions doped Na 2 O-ZnO-Al 2 O 3 -B 2 O 3 (BAZN) glasses with variable doping concentrations were synthesized by melt-quenching technique. The XRD pattern reveals amorphous nature of the as-synthesized glass. The FT-IR spectrum reveals various stretching and bending vibration of aluminates, borate and some other groups. The emission spectra exhibit two intense bands at around 482 nm (blue) and 575 nm (yellow) corresponding to the 4 F 9/2  →  6 H 15/2 and F 9/2  →  6 H 13/2 transitions respectively. The CIE chromaticity coordinates of the as-synthesized glasses are lying in white region and in proximity to the coordinates for white light specified by National Television Standard Committee and commercial phosphor converted white light emitting devices. The decay profile of BAZN glasses showed bi-exponential behavior due to the energy transfer mechanism from excited donor ion to unexcited acceptor ion. The above-mentioned studies show potential of the as-synthesized Dy 3+ doped BAZN glasses in solid state lighting applications. [ABSTRACT FROM AUTHOR]

A series of Mn(II)-doped hardystonite phosphors was obtained by using a sol-gel technique. Structural, morphological, and optical properties of the prepared samples were investigated by X-ray diffraction, Fourier transform infrared, scanning electron microscopy and diffuse reflectance spectrum. The photoluminescence excitation and emission spectra of the prepared phosphors exhibited a strong band at ~ 254 nm and an intensified emission band at ~ 525 nm, respectively. Of all the prepared phosphors, 0.03Mn(II) doped hardystonite phosphor possessed a highly intense emission band, which demonstrated that 0.03 mol was the optimized concentration of Mn(II) ions. All the prepared phosphors emitted a bright green color, as confirmed by the Commission International de I′Eclairage co-ordinates. Electron paramagnetic resonance study suggested the existence of Mn(II) ions at sites with octahedral symmetry (g value ~2) and the dominance of covalent bonding in the prepared phosphors. [ABSTRACT FROM AUTHOR]

A series of calcium aluminate phosphors doped with Tm3+ ions at various molar concentrations was prepared via sol-gel route. Various characterizations were conducted to identify the structural and luminescence properties. The XRD patterns of the prepared series suggested that the pure phase was attained. Fourier transform-IR spectrum was recorded to identify various bonds involved in the structure of calcium aluminate. Diffuse reflectance was studied and a Tauc plot was prepared to determine the band gap. Photoluminescence studies were conducted to check the viability of the prepared material in w-LEDs. The prepared calcium aluminate phosphors exhibited 459 nm emission under n-UV excitation. The evaluated CIE coordinates showed core blue emission with high color purity. All the investigations carried out for the prepared phosphors suggested their potential for application as blue emitters in w-LEDS. [ABSTRACT FROM AUTHOR]

A series of CaY 2 Al 4 SiO 12 garnet phosphor doped with different concentrations of Sm3+ varying from 0.01 mol to 0.11 mol was prepared by using the sol-gel method. Structural investigations were conducted by recording the X-ray diffraction (XRD) patterns. The UV-Vis diffuse reflectance spectrum was recorded to identify the optical band gap. The luminescence behavior was studied by recording the excitation and emission spectra. The emission spectra recorded under 403 nm excitation revealed emission peaks due to f-f transitions of Sm3+ ions. The optimum amount of Sm3+ was also identified by studying the concentration effect. The studied colorimetric properties revealed the orange color emission of the prepared garnet phosphors. These results support the potential utility of the prepared garnet phosphor in display and lighting devices. [ABSTRACT FROM AUTHOR]

Gadolinium doped calcium magnesium silicate phosphor was prepared with varying amounts of gadolinium in the host lattice from 0.005 mol to 0.09 mol. X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) images were recorded to understand the structure and texture of the prepared phosphors. The phosphor's luminescent properties were characterized by recording their excitation and emission spectra. The effect of Gd3+ ion concentration in the host lattice was studied to identify the optimum concentration of Gd3+ ions for the most effective luminescence. The optimum concentration was found to be 0.05 mol. Local environmental effect on the Gd3+ ions in the host was studied by recording the material's electron paramagnetic resonance (EPR) spectra. The EPR spectra revealed several resonance signals with g values in the range 2–6 for the prepared phosphors. [ABSTRACT FROM AUTHOR]

Terbium (Tb3+) ions doped calcium aluminozincate (CAZ) phosphors with different concentration of Tb3+ ions (0.0–5.0 mol%) have been successfully prepared by sol-gel method. The crystal phase analysis and morphology of the as prepared phosphors have been studied from X-ray diffraction (XRD) patterns and field emission scanning electron microscope (FE-SEM) image. The luminescence behaviour of Tb3+ doped CAZ phosphors have been studied relative to variable dopant ion concentration. The intense emission has been observed at 543 nm under 238 nm excitation for all the phosphors. The decay curve analysis manifests the energy transfer as a consequence of dipole-dipole interaction between Tb3+ ions in the host. The colorimetric property has been understood on the basis of evaluated CIE color coordinates. The systematic study of Tb3+ doped CAZ phosphors determine the potential utility of these phosphors in lighting and display applications. Partial energy level diagram of Tb3+ ion in CAZ phosphor. Image 1 • Tb3+ ions doped calcium aluminozincate phosphors synthesized by sol-gel method. • Transition from 5D 3 and 5D 4 levels exhibit emission in blue and green regions. • Energy transfer from 5D 3 to 5D 4 energy level at 4.0 mol%. enhance green emission. • Color tunability is achieved in Tb3+ doped as synthesized phosphors. • These studies suggest the utility of above mentioned phosphors in lighting and display devices. [ABSTRACT FROM AUTHOR]

MgY 2-x Al 4 SiO 12 :xCr3+ garnet phosphors doped with different concentrations of Cr3+ (0.01–0.07 mol) were prepared using the sol-gel method, and their structural, luminescent, and electron paramagnetic resonance (EPR) properties were studied. Structural and morphological measurements were made by powder X-ray diffraction and scanning electron microscope, respectively. Cubic-structured garnet phosphors were observed. The diffuse reflectance spectrum of 0.02 mol Cr3+ doped MgY 2 Al 4 SiO 12 phosphor was studied to estimate the crystal field parameters (Dq and B). The emission spectrum depicts intense emission in the far-red region under 580 nm excitation. The optimized concentration of Cr3+ ions is identified as 0.02 mol, for which the emission intensity is maximum. The CIE coordinates measured from the emission spectra for the as-prepared phosphors fall in the red region of the visible spectrum. The EPR spectra recorded at room temperature reveal five g -values at ~3.90, ~3.57, ~2.67, ~2.46, and ~1.97, corresponding to isolated Cr3+ ions and exchange-coupled Cr3+-Cr3+ pairs. • By sol-gel synthesis, Cr3+ incorporated MgY 2 Al 4 SiO 12 matrix obtained. • Prepared phosphors characterized using XRD, SEM, EPR, UV–Vis and PL spectroscopy. • Upon 580 nm light excitation, far-red region 689 nm emission observed. • EPR reveal five g -values corresponding to isolated Cr3+ ions and exchange-coupled Cr3+–Cr3+ pairs. [ABSTRACT FROM AUTHOR]

We investigated the structural and luminescence characteristics of Ba 2 YZrO 6 :xGd (0.01 ≤ x ≤ 0.11) perovskite ceramic phosphors prepared by sol-gel with dominating cubic phase. The Fourier transform infrared (FT-IR) spectrum depicted various shoulders attributed to the functional groups present in the host matrix. The photoluminescence (PL) spectroscopy exhibited the emission at 315 nm under the excitation of 229 nm light, owing to the P 6 7 / 2 → S 8 7 / 2 transition. We also observed concentration quenching in the prepared phosphor. Further, the electron paramagnetic resonance (EPR) spectra recorded for the samples under room temperature discerning three main resonance signals with effective g-values 6.02, 2.45, and 1.32. [ABSTRACT FROM AUTHOR]

Sm3+-doped CaAl 4 O 7 phosphor has been synthesized using the sol-gel method with a varying doping concentration of Sm3+ ions. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images were used to study the structural and morphological properties of the material. The UV-VIS-NIR spectrum was also recorded to analyze the optical transitions of CaAl 4 O 7 phosphor doped with Sm3+ ions. The photoluminescence (PL) spectra of the phosphors were also recorded to examine the luminescence properties. The PL spectra exhibit intense orange emission at 602 nm that was obtained for the prepared samples using the 403 nm excitation. The optimized concentration of Sm3+ ions in CaAl 4 O 7 was found to be 0.03 mol, beyond which concentration quenching was observed. The CIE color chromaticity coordinates of all the synthesized phosphors lie in the orange region of the chromaticity diagram. All of these results indicate the candidature of CaAl 4 O 7 phosphor doped with Sm3+ ions for lighting and display applications. Image 1 • The orange-emitting Sm3+ doped CaAl 4 O 7 phosphor obtained via sol-gel method. • The Sm3+ emission is quenched at 0.03 mol. • Synthesized phosphor could be a potential material for lighting and display applications. [ABSTRACT FROM AUTHOR]

Tb3+ activated Na 3 YSi 2 O 7 phosphor for different amounts of Tb3+ ions were developed using sol-gel process. Structural analysis was conducted using Fourier Transform Infrared (FT-IR) spectroscopy and X-ray diffractograms. Further, luminescence behavior was analyzed by recording excitation and emission spectra of the mentioned phosphors. To obtain insight into the luminescence characteristics, these phosphors were excited under VUV wavelength (147 and 172 nm) along with UV excitation of 234 nm to elucidate the emission behavior. Colorimetric and photometric analyses were also conducted to establish the visible emission of the sol-gel derived phosphors. The photoluminescence study reflected the utility of Tb3+ doped Na 3 YSi 2 O 7 phosphor in plasma display panels. [ABSTRACT FROM AUTHOR]

The citrate sol-gel method was used to synthesize a set of KNa 3 Al 4 Si 4 O 16 :xTb3+ phosphors (x = 0.005, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13 mol). Powder X-ray diffraction (XRD) was carried out for structural investigations and Fourier transform infrared (FT-IR) spectra for identification of functional groups. The crystallite size of the phosphors was estimated by employing the well-known Debye-Scherer equation. Scanning electron microscopy (SEM) was performed to gather the morphological information. For photoluminescence (PL) studies, excitation and emission spectra were recorded for different concentrations of trivalent terbium (Tb3+) ion. Commission International de I′Eclairage (CIE) coordinates were calculated. The results confirmed the green emission from the prepared samples and the potential of this candidate as a green emitter for lighting applications. [ABSTRACT FROM AUTHOR]

CaLa 4 Si 3 O 13 phosphors were successfully prepared by the sol-gel method by incorporating different amounts of Gd3+ ions as dopant. The crystalline phase and compositional arrangement of the host lattice were elucidated by XRD and FT-IR. The crystal sizes of the prepared samples were evaluated using the Scherrer formula. The luminescent properties of the CaLa 4 Si 3 O 13 :Gd3+ phosphors were studied by using PL spectroscopy. The electron paramagnetic resonance spectra of the sample revealed resonance signals arising on account of Gd3+ ion occupancy at sites with low symmetry. The studies conducted for the prepared samples confirmed that Gd3+ ions in the CaLa 4 Si 3 O 13 matrix are useful as UVB emitters. [ABSTRACT FROM AUTHOR]