Electronic Materials Research Laboratory

Thiruvananthapuram, India

Electronic Materials Research Laboratory

Thiruvananthapuram, India
SEARCH FILTERS
Time filter
Source Type

Pazhani R.,Electronic Materials Research Laboratory | Padma Kumar H.,Wmo Arts And Science College | Moses Ezhil Raj A.,Scott Christian College | Solomon S.,St Johns College | Thomas J.K.,Electronic Materials Research Laboratory
Journal of Alloys and Compounds | Year: 2011

Phase pure zirconium oxide powders have been synthesized using the single step auto-ignition combustion method, the particles were nanometer sized (20 nm) and the size distribution was very narrow (3.4 nm). Systematic structural characterization revealed the t-ZrO 2 and indexed for its tetragonal structure (a = 3.5975 and c = 5.1649 ). Calculated microstrain in most of the plane indicated the presence of compressive stress (65-288 MPa) along various planes of the particles. Observed space group (P4 2/nmc) revealed the presence of cations in the 8e positions (0.75, 0.25, 0.75) and the anions in the 16 h positions (0.25, 0.25, 0.4534). The metal-oxide (Zr-O) band observed at the low wavenumber region further confirmed the phase purity of the as-prepared ZrO 2 nanopowders. Peaks at the binding energy positions 2.042 and 0.525 keV in the energy dispersive X-ray spectrum revealed oxygen deficient zirconia. The particle size estimated by TEM was in good agreement with the results obtained through X-ray line broadening (20.81 nm) measurements. The nanopowders were sintered to above 98% of the theoretical density by using vacuum sintering technique at a relatively low temperature of 1300 °C. Stable tetragonal ZrO 2 experimentally yield the permittivity value of about 28 at 10 MHz. © 2011 Elsevier B.V. All rights reserved.


Deepa A.S.,Electronic Materials Research Laboratory | Vidya S.,Electronic Materials Research Laboratory | Manu P.C.,Electronic Materials Research Laboratory | Solomon S.,St Johns College | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

Nanocrystalline Barium stannate (BaSnO3) was synthesized through auto-ignited combustion technique. The X-ray diffraction studies of BaSnO 3 nanoparticles reveals that the nanopowder is single phase, crystalline, and has a cubic perovskite structure with a lattice constant a = 4.115 . The average particle size calculated from full width half maximum (FWHM) using Scherer formula is ∼25 nm. The phase purity of the powder was further examined using Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopic techniques. XRD pattern of BaSnO3 was refined for atomic coordinates, lattice parameters and occupancies using Rietveld analysis. Vibrational analysis of sample shows that there is a phase transition from distorted cubic to ideal cubic structure during heat treatment. The thermal stability of BaSnO3 nanopowder has been confirmed using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The particle size of the as-prepared powder from transmission electron microscopy was found to be in the range 20-30 nm. The absorption spectra and photoluminescence spectra of the sample were also studied. The band gap determined was 2.887 eV and found to be a semiconductor. © 2010 Elsevier B.V. All rights reserved.


Mathew C.T.,Electronic Materials Research Laboratory | Solomon S.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Materials Today: Proceedings | Year: 2015

In this paper we report the synthesis of MgAl2O4 (Spinel) by a modified auto-igniting combustion technique for the first time. The as prepared powder is phase pure and the average grain size is around 16nm with well defined lattice planes. The vibrational spectroscopic studies confirm the structure of the sample. The spinel ceramic pellet sintered to 98.5% of the theoretical density shows a transmittance of 71% in the visible region and 65% in the mid-infrared region, which can be further improved by polishing and consequently found applications as infrared transparent windows and domes. © 2015 Elsevier Ltd.


Rejith P.P.,Electronic Materials Research Laboratory | Vidya S.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Materials Today: Proceedings | Year: 2015

The optimization of flux line pinning in superconductors is one of the most efficient ways to improve the transport properties of these materials. In this work, we have examined the effectiveness of an insulating nano particle inclusion in a type II superconductor as a pinning center with a size close to the coherence length, ξ. We report on measurements of the superconducting properties of YBa2Cu3O7-δ bulk superconductors with different weight % of nano particles of TiO2 contents (x = 0-3wt %) prepared by the modified combustion route. The microstructure of bulk YBCO added with nano particles was characterized by scanning electron microscopy. Sub-micron, randomly oriented particles of this phase were found to form around grain boundaries and within YBCO grains in bulk sintered pellets. It is observed that the critical current density is higher by a factor of 3 and the Jc-B behavior is remarkably improved in samples with nano additions. However, the superconductor transition temperature (Tc) slightly decreases from 92K to 90.5K. The flux pinning force is enhanced by 8 times that of pure YBCO sample. Thus these nano particles are effective flux pinning centers and enhance the transport critical current density at liquid nitrogen temperature for an applied magnetic field. The experimental results suggest that the added nano-sized TiO2 particle may have high pinning efficiency at a temperature around 77K. © 2015 Elsevier Ltd.


Vidya S.,Electronic Materials Research Laboratory | Solomon S.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Materials Today: Proceedings | Year: 2015

Nanocrystalline AMo0.5W0.5O4 (A= Ba, Sr, Ca) have been synthesized through a modified combustion process. The X-ray diffraction studies have revealed that the samples are single phase and possess tetragonal structure. Raman spectra showed that the Ag modes of [MoO4]2- and [WO4]2- are split up into two well distinguished peaks while that of Bg and Eg modes of the tetrahedral units superimposed to form single strong peaks. Corresponding Au and Eu modes are registered in FTIR spectra. Vibrational analysis also confirms the long range order of lattice structure. The nanocyrstalline AMo0.5W0.5O4 are found to be excellent photo luminescent materials with strong blue and green emission. Blue emission is attributed to [WO4]2- and green emission responds to [MoO4]2- units. Thus we can fine tune the emission wavelength from blue to green region by varying the composition. These nanocrystals could be sintered at a relatively low temperature in the range 830-875oC for 3h to a high density. The SEM image of the sintered material indicates high densification of the material. The room temperature dielectric constant (e{open}r) and of the sintered pellet at 5MHz were above ~12 and attains a maximum value of ~15. The low sintering temperature, moderate dielectric constant, low loss factor t makes nano AMo0.5W0.5O4 excellent composition for low temperature cofired ceramics, substrate material, and electronic packing materials, besides numerous optical applications. © 2015 Elsevier Ltd.


Mathew C.T.,Electronic Materials Research Laboratory | Solomon S.,Electronic Materials Research Laboratory | Koshy J.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Ceramics International | Year: 2015

Abstract Synthesis of nano particles of yttria (Y2O3) ceramics (∼15 nm) by a single step auto-igniting combustion technique, followed by sintering of the sample by three variants of sintering methods viz. resistive, microwave and microwave hybrid heating to optimum density and their remarkable infrared transmission characteristics are presented in this paper. In microwave hybrid sintering there was a considerable reduction in the sintering temperature and the soaking time compared to the resistive and microwave sintering. The pellets sintered by microwave hybrid heating at 1450°C for 20 min achieved a density 99.2% of the theoretical density with reduced average grain size of 220 nm and the pellet showed enhanced transmittance of ∼80% in the visible and ∼80% in the mid infrared region. The results clearly indicate that the yttria ultra fine nanophase powder synthesised by the single step combustion method and sintered via microwave hybrid heating shows better transmittance properties and can be used very effectively for the fabrication of infrared transparent windows and domes. © 2015 Elsevier Ltd and Techna Group S.r.l.


Vidya S.,Electronic Materials Research Laboratory | Solomon S.,St Johns College | Thomas J.K.,Electronic Materials Research Laboratory
Journal of Electronic Materials | Year: 2013

Nanocrystalline scheelite CaWO4, a promising material for low-temperature co-fired ceramic (LTCC) applications, has been successfully synthesized through a single-step autoignition combustion route. Structural analysis of the sample was performed by powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and Raman spectroscopy. The XRD analysis revealed that the as-prepared sample was single phase with scheelite tetragonal structure. The basic optical properties and optical constants of the CaWO4 nanopowder were studied using ultraviolet (UV)-visible absorption spectroscopy, which showed that the material was a wide-bandgap semiconductor with bandgap of 4.7 eV at room temperature. The sample showed poor transmittance in the ultraviolet region but maximum transmission in the visible/near-infrared regions. The photoluminescence spectra recorded at different temperatures showed intense emission in the green region. The particle size estimated from transmission electron microscopy was 23 nm. The feasibility of CaWO4 for LTCC applications was studied from its sintering behavior. The sample was sintered at a relatively low temperature of 810 C to high density, without using any sintering aid. The surface morphology of the sintered sample was analyzed by scanning electron microscopy. The dielectric constant and loss factor of the sample measured at 5 MHz were found to be 10.50 and 1.56 × 10-3 at room temperature. The temperature coefficient of the dielectric constant was -88.71 ppm/ C. The experimental results obtained in this work demonstrate the potential of nano-CaWO4 as a low-temperature co-fired ceramic as well as an excellent luminescent material. © 2012 TMS.


Vidya S.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
IOP Conference Series: Materials Science and Engineering | Year: 2015

Nano crystalline PbMoO4 was synthesized through an auto-ignited combustion technique. The X-ray diffraction studies of PbMoO4 nanoparticles reveals that the as-prepared powder itself is single phase and possess tetragonal structure. The average particle size of the as-prepared powder calculated using scherrer formula is 28nm. Fourier transform Infrared spectrum shows that the as prepared powder itself is phase pure with no formation of secondary phase .The optical band gap determined from UV-Visible absorption spectra is 3.20eV.Photoluminescence spectra of the samples shows blue emission. © Published under licence by IOP Publishing Ltd.


Vidya S.,Electronic Materials Research Laboratory | Solomon S.,St Johns College | Thomas J.K.,Electronic Materials Research Laboratory
Journal of Materials Science: Materials in Electronics | Year: 2014

Nanocrystalline strontium tungstate (SrWO4) is synthesized through a single step modified combustion process. The X-ray diffraction, Fourier transform Raman and Infrared spectroscopy studies reveal that the as-prepared powder is single phase and possess tetragonal structure. The transmission electron microscopic investigations have shown that the particle size of the as prepared powder is in the range 18-22 nm. The optical constants are estimated from the UV-Visible studies and calculated optical band gap is 4.28 eV. The sample showed maximum transmission in the visible regions but poor transmittance in the ultraviolet region. The photoluminescence spectra recorded at different temperatures showed intense blue emission. The nanocrystalline SrWO4 obtained by the present combustion method was sintered to 95 % density at a relatively lower temperature of 810 C for 3 h. The dielectric constant (εr) and loss factor (tan δ) of the sintered SrWO4 pellets at 5 MHz measured at room temperature were 9.9 and 6.29 × 10-3 respectively. The experimental results obtained in this work demonstrate the application of SrWO4 as UV filters, transparent films for window layers on solar cells, anti-reflection coatings, scintillators, detectors and for low-temperature co-fired ceramic applications. © 2013 Springer Science+Business Media New York.


Vidya S.,Electronic Materials Research Laboratory | Solomon S.,St Johns College | Thomas J.K.,Electronic Materials Research Laboratory
Physica Status Solidi (A) Applications and Materials Science | Year: 2012

The synthesis of nanocrystalline calcium molybdate (CaMoO 4) through an autoigniting combustion technique is reported in this paper. The structural characterization of the as-prepared nanocrystallites were done by X-ray diffraction (XRD), Fourier transform Raman, and Fourier transform infrared (IR) spectroscopy and the morphological studies using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The studies reveal that the as-prepared powder itself was phase pure with tetragonal structure and of particle size 25 nm. The sample was sintered at a relatively low temperature of 775 °C to a high density of ∼95% for the first time, without the use of any sintering aid. The optical bandgap energy calculated from the ultraviolet-visible absorption spectrum for the as-prepared and annealed sample was 3.72 and 3.99 eV, respectively. The photoluminescence spectra of the sample showed an intense emission in the green region (528 nm). The dielectric constant and loss factor of the sample at 5 MHz was found to be 11.00 and 6.40 × 10 -3 at room temperature. The temperature coefficient of dielectric constant was -95.04 pp/°C. These observations reveal that nanostructured CaMoO 4 is a promising scheelite low-temperature co-fired ceramic (LTCC) and also an excellent luminescent material. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Loading Electronic Materials Research Laboratory collaborators
Loading Electronic Materials Research Laboratory collaborators