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A series of Mn2+ activated Sr2ZnSi2O7 phosphors with variable Mn2+ ions concentration were prepared via citrate sol–gel method. The systematic analysis of structure and luminescent properties were carried out by recording x-ray diffraction patterns, scanning electron micrographs, excitation and emission spectra along with electron paramagnetic resonance (EPR) spectra. The optimization of Mn2+ ion concentration in the synthesized phosphors was done by analyzing emission spectra. The Mn2+ activated Sr2ZnSi2O7 phosphors exhibit green emission under 263 nm excitation. The EPR spectra exhibit sextet hyperfine lines with resonance at g ≈ 2.0 indicating tetrahedral symmetry and covalent bonding between Mn2+ ions and O2− ligand ions bound to it. All the aforesaid results support the suitability of Mn2+ activated Sr2ZnSi2O7 phosphors as visible green emitters in optoelectronic display devices. [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 strontium silicate (Sr2SiO4:xGd3+; 0.01 ≤ x ≤ 0.11) systems have been synthesized via sol-gel technique. The structural, morphological, luminescent, and magnetic properties have been investigated using X-ray diffraction patterns, scanning electron microscopy (SEM), photoluminescence (PL), and electron paramagnetic resonance (EPR) technique, respectively. The synthesized strontium silicate samples exhibit a mixed phase of α′ and β-Sr2SiO4. The SEM images show irregular morphologies with a random distribution of particles. The PL spectra confirm the ultraviolet emission from the synthesized samples and the optimum concentration of Gd3+ ions is observed at 0.05 mol. With low dopant concentrations, Sr2SiO4:Gd3+ sample displays EPR lines, mainly in the low field region with effective g-values 5.8, 4.5, 3.1, and 2.7. As dopant concentration increases, a broad line appears with geff ~ 2.1 along with the low field lines. A relatively strong crystal field is experienced by Gd3+ ion due to distortions in the immediate environment of the ion, which lead to low field EPR lines. These studies allow the use of gadolinium-activated strontium silicate in phototherapy lamps. [ABSTRACT FROM AUTHOR]

A series of Pb 2+ -doped SrZrO 3 phosphors with a varying Pb 2+ concentration has been successfully synthesized using the sol-gel method. The structural, morphological, and luminescence properties along with the electron paramagnetic resonance (EPR) properties have been investigated in details. The structural analysis was carried out by recording X-ray diffraction (XRD) patterns, which confirms the pure-phase formation of the synthesized phosphors. The morphological study was performed using a scanning electron microscope (SEM) that showed micron-sized particles with irregular morphologies. The photoluminescence excitation and emission spectra were also recorded. The emission intensity shows the maximum at 360 nm that was pumped at 278 nm for SrZrO 3 :Pb 2+ . The optimized Pb 2+ concentration is 0.015 mol. Investigations of un-doped and Pb 2+ doped SrZrO 3 phosphor have been carried out using electron paramagnetic resonance (EPR) technique. Pure SrZrO 3 exhibits an axially symmetric EPR line with g || = 1.93 and g ⊥ = 1.99. These lines are ascribed to Zr 3+ ion. Additional lines are not observed in the Pb 2+ doped phosphors. [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 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]

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]

A series of Er3+-doped Sr 2 La 8 (SiO 4) 6 O 2 phosphors was prepared by the sol-gel route. Prepared samples were characterized by X-ray diffraction, Fourier transform infrared, and diffuse reflectance spectroscopy techniques. The optical properties of the prepared phosphors were studied from down conversion photoluminescence (PL) excitation and emission spectra. Further, to ascertain the emission color of the prepared samples, the CIE coordinates obtained using emission spectra, which clearly revealed the green emission from the prepared Er3+-doped Sr 2 La 8 (SiO 4) 6 O 2 phosphors. These results suggest the potential utility of the prepared oxyapatite structured phosphors for photonic device 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]

In this study, the sol-gel method was used to synthesis highly crystalline, Er3+-doped Ca 2 La 8 (SiO 4) 6 O 2 phosphors. XRD, SEM and FT-IR analysis were conducted to determine the phase, surface morphology and bond formation inside the host lattice. The results of diffuse reflection studies of the samples were matched well with the PL excitation studies. Under 379 nm UV excitation, these phosphors exhibited intense green emission. PL studies conducted on the prepared phosphors revealed that at high concentration of the doped rare earth (RE) ion, the distance between Er3+-Er3+ decreased, leading to the formation of clusters. Such clusters induced non-radiative energy losses in the prepared phosphors. These investigations conducted on the prepared phosphor demonstrate its utility in the area of solid-state lighting (SSL). [ABSTRACT FROM AUTHOR]

A batch of Ho3+-doped Sr 2 La 8 (SiO 4) 6 O 2 phosphors with holmium ion dopant concentration ranging from 0.01 to 0.11 mol was synthesized successfully using the sol-gel method. The structural information was gathered by studying X-ray diffraction (XRD) patterns and Fourier transform infrared (FT-IR) spectroscopy. The optical properties were explored using diffuse reflectance (DRS) and photoluminescence (PL) spectral measurements. The colorimetric behavior was determined using emission spectra to obtain the CIE coordinates. The optimized Ho3+ dopant concentration was 0.05 mol in the Sr 2 La 8 (SiO 4) 6 O 2 host. The prepared phosphors emitted green color in visible domain and thus have potential applications in w-LEDs lighting and displays. [ABSTRACT FROM AUTHOR]