Entity

Time filter

Source Type


Pavani K.,Sri Venkateswara University | Suresh Kumar J.,University of Aveiro | Rama Moorthy L.,Sri Venkateswara University | Rama Moorthy L.,Chadalawada Ramanamma Engineering College
Journal of the American Ceramic Society | Year: 2014

Dy3+-Tm3+ ions codoped SrMg2La 2W2O12 (strontium magnesium lanthanum tungstate) phosphors were synthesized by conventional high-temperature solid-state reaction method. X-ray analysis of the end products revealed the well-crystallized phases with orthorhombic structure. The functional groups present in the phosphors were studied by the Fourier transform infrared measurements. To know the potential applicability of these phosphors for white light emission, the excitation and emission spectra were recorded. The excitation spectra exhibited an intense broad band at 313 nm, pertaining to the O → W ligand-to-metal charge-transfer state (LMCT) of the host. With the excitation of LMCT band (313 nm), the decay curves of singly doped SrMg 2La2W2O12:Dy phosphors exhibited single exponential, where as the codoped SrMg2La2W 2O12:DyTm phosphors exhibited double exponential nature. The luminescence colors of these phosphors were estimated from Commission Internationale de L'Eclairage (CIE) coordinates using the photoluminescence data. The color of singly doped SrMg2La2W 2O12:Dy phosphor has been tuned by codoping with Tm 3+ ions. It has been noticed that the CIE chromaticity coordinates (x,y) determined from the luminescence spectrum of singly Dy3+ doped SrMg2La2W2O12 phosphor shifted toward the white light region, when codoped with Tm3+ ions. The increase in correlated color temperatures (Tcct) has been noticed with the increase of Tm3+ ions concentration in SrMg 2La2W2O12:DyTm phosphors. © 2014 The American Ceramic Society. Source


Chengaiah T.,Sri Venkateswara University | Jayasankar C.K.,Sri Venkateswara University | Pavani K.,Sri Venkateswara University | Sasikala T.,Sri Venkateswara University | And 2 more authors.
Optics Communications | Year: 2014

Different concentrations of Dy3+ ions activated ZnMoO 4 luminescent phosphors were prepared using the solid-state reaction method by sintering at 900 C. Phase purity features of the prepared phosphors were characterized by X-ray diffraction (XRD) patterns and the particle size has been found to be about 40 nm. The compositional and structural details were carried out using Fourier transform infrared (FTIR) spectrum. The characteristic emission peaks of Dy3+ ions were observed due to the 4F9/2→6H15/2 (490 nm) and 4F9/2→6H13/2 (580 nm) transitions. The variation of luminescence intensity with Dy3+ ions concentrations as well as with different excitation wavelengths has been discussed. The CIE chromaticity color coordinates (x, y) were calculated from the luminescent characteristics of ZnMoO4: Dy3+ phosphors, which fall in the white light region of the chromaticity diagram. The lifetime of 4F9/2 excited level has been quenched due to the energy transfer among Dy3+ ions at higher concentrations. © 2013 Elsevier B.V. Source


Lokeswara Reddy G.V.,Sri Venkateswara University | Rama Moorthy L.,Sri Venkateswara University | Rama Moorthy L.,Chadalawada Ramanamma Engineering College | Jamalaiah B.C.,University of Aveiro | Sasikala T.,Sri Venkateswara University
Ceramics International | Year: 2013

A series of YAl3(BO3)4 phosphors doped with different concentrations of Dy2O3 (0.1≤x≤5 mol%) were prepared by solid-state reaction method. The crystallization process of the precursor has been examined by differential thermal analysis (DTA) measurements. The phase purity and surface morphological features were characterized by X-ray diffraction (XRD) and scanning electron microscopic (SEM) investigations. The YAl3(BO3)4 nanocrystals obtained were found to be about 45 nm in size and have the trigonal structure with some agglomeration. Fourier transform infrared (FTIR) and energy dispersive X-ray spectra (EDS) measurements were carried out to understand the compositional and elemental analysis. The characteristics emission peaks of Dy3+ ion corresponding to the transitions of 4F 9/2→6H15/2 at 485 nm and 4F9/2→6H13/2 at 576 nm were observed in the emission spectra. The luminescence quenching noticed at higher Dy2O3 concentrations is due to the exchange interaction among the excited Dy3+ ions. © 2012 Elsevier Ltd and Techna Group S.r.l. Source


Chengaiah T.,Sri Venkateswara University | Jayasankar C.K.,Sri Venkateswara University | Rama Moorthy L.,Sri Venkateswara University | Rama Moorthy L.,Chadalawada Ramanamma Engineering College
Physica B: Condensed Matter | Year: 2013

Ce-Eu co-activated Na3Gd(PO4)2 phosphors of high luminescence efficiency were prepared by the solid state reaction method. Emission properties and the partical size of the synthesized phosphors have been explored by the photoluminescence (PL) and X-ray diffraction measurements. The CIE chromaticity color coordinates (x, y) were calculated from the emission spectra of Na3Gd(PO4)2:Ce 3+/Eu3+ phosphors, which fall in the white light region of the chromaticity diagram. The energy transfer from the excited Ce3+ to Eu3+ ions has been explained. © 2013 Published by Elsevier B.V. Source


Ramachari D.,Sri Venkateswara University | Rama Moorthy L.,Sri Venkateswara University | Rama Moorthy L.,Chadalawada Ramanamma Engineering College | Jayasankar C.K.,Sri Venkateswara University
Materials Research Bulletin | Year: 2013

Sm2O3-doped oxyfluorosilicate glasses were prepared by melt-quenching method. The differential thermal analysis and X-ray diffraction were carried out to investigate the glass transition temperature and structure of precursor glass. Infrared spectroscopy, Raman, optical absorption, photoluminescence and decay measurements were carried out for Sm 3+-doped oxyfluorosilicate glasses. From the absorption spectrum, the Judd-Ofelt intensity parameters have been evaluated to predict the radiative properties for the emission levels of Sm3+ ions. The lifetimes of 4G5/2 level are found to decrease from 1.17 to 0.93 ms due to the energy transfer, when the concentration of Sm3+ ions increases from 0.1 to 2.0 mol%. The optical gain parameter (18.13 × 10-25 cm2 s) of the investigated glass is found to be higher than the other Sm2O3-doped glass systems. © 2013 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations