Structural and optical properties of green emitting Y_(2)SiO_(5):Tb^(3+) and Gd_(2)SiO_(5):Tb^(3+) nanoparticles for modern lighting applications

The optical and structural properties of Tb^(3+)-doped yttrium and gadolinium oxyorthosilicate(Y_(2)SiO_(5) and Gd_(2)SiO_(5)) phosphors were analyzed.The samples were synthesized via sol-gel combustion method using organic fuel.The phase purity and structural properties of the samples were determined via combined approach of powder X-ray diffraction,Fourier transformation infrared(FTIR) and transmission electron microscopy(TEM).X-ray measurements revel monoclinic crystal lattice with P_(21/c) symmetry for both M_(2)SiO_(5)(pure host) and M_(2)SiO_(5):Tb^(3+)(doped) silicates,irrespective of the nature of metal(Y or Gd),presence or absence of Tb^(3+)in lattice and change in calcination temperature up to 1050℃.FTIR analysis was applied to confirm the bonding of prepared materials.The appearance of bands corresponding to SiO_(4) tetrahedra(880-1020 cm^(-1)) suggest the layered structure and support the diffraction measurements.TEM micrographs confirm the synthesis of spherical nanoparticles with filled morphology,narrow size distribution and slightly agglomerated crystallites of the samples.The elemental composition of prepared materials was determined using energy dispersive X-ray spectroscopy.The spectra show peaks only for elements assimilated within the host framework.The photoluminescence(PL) emission spectra of Tb^(3+)-doped samples show ^(5)D_(4)→^(7)F_(J)(J=3-6) transitions under 254 nm-excitation.The dominant peak at 544 nm for ^(5)D_(4)→^(7)F_(5) transition is responsible for the emission of green light on ultraviolet-visible excitation in both the Tb^(3+)-doped host matrixes.Owing to advantageous properties like intense PL and high crystallinity,these nanophosphors could possess potential applications in the mercury free lighting sources and optoelectronic devices.

Synthesis and spectroscopic investigations of trivalent europium- doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) nanophosphors for display applications

To explore the silicate lattice-based nanophosphors, a series of Eu3+-doped Z_(2)Si_(3)O_(8)(Z = Mg, Ca and Sr) materials were prepared by sol–gel procedure. The metal nitrates and silica powder were used as precursor components for the synthesis of these luminescent materials. Photoluminescence(PL) emission spectra, powder X-ray diffraction(PXRD), energy-dispersive X-ray spectroscopy(EDS), Fourier transform infrared spectroscopy(FTIR) and transmission electron microscopy(TEM)spectroscopic techniques were applied for the characterization of the fabricated materials. Three peaks were observed at 589, 613 and 650–652 nm corresponding to ^(5)D_(0)→^(7)F_(1-3) transition in PL emission spectra. Upon395 nm excitation and at 0.03 mol Eu3+, these nanophosphors displayed optimum photoluminescence with the most intense peak analogous to ^(5)D_(0)→^(7)F_(2)transition of dopant ion. The as-prepared phosphor materials were re-heated at1050 and 1150 ℃ to observe the consequences of higher temperatures on the emission intensity and crystal lattice.XRD analysis confirmed that all the synthesized materials were of crystalline nature, and the crystallinity was observed to be improved by increasing the temperature. In the FTIR spectrum, peaks at 483 and 610 cm^(-1) proved the existence of SiO_(4)group in Ca_(2)Si_(3)O_(8), and the peak centered at 417 cm^(-1) confirmed the presence of MgO6 octahedral in Mg_(2)Si_(3)O_(8) materials. TEM images were used to determine the particle size(13–35 nm) and to study the threedimensional structure of nanophosphor materials. The experimental studies indicate that these materials may be promising as red-emitting nanophosphors for white lightemitting diodes.