Dielectric Materials Research Laboratory

Anchal, India

Dielectric Materials Research Laboratory

Anchal, India

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Vidya S.,Electronic Materials Research Laboratory | Solomon S.,Dielectric Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Advances in Condensed Matter Physics | Year: 2013

Synthesis of nano-BaWO4 by a modified combustion technique and its suitability for various applications are reported. The structure and phase purity of the sample analyzed by X-ray diffraction, Fourier transform Raman, and infrared spectroscopy show that the sample is phase pure with tetragonal structure. The particle size from the transmission electron microscopy is 22 nm. The basic optical properties and optical constants of the nano BaWO4 are studied using UV-visible absorption spectroscopy which showed that the material is a wide band gap semiconductor with band gap of 4.1 eV. The sample shows poor transmittance in ultraviolet region while maximum in visible-near infrared regions. The photoluminescence spectra show intense emission in blue region. The sample is sintered at low temperature of 810°C, without any sintering aid. Surface morphology of the sample is analyzed by scanning electron microscopy. The dielectric constant and loss factor measured at 5 MHz are 9 and 1.56 × 10 - 3. The temperature coefficient of dielectric constant is -22 ppm/°C. The experimental results obtained in the present work claim the potential use of nano BaWO4 as UV filters, transparent films for window layers on solar cells, antireflection coatings, scintillators, detectors, and for LTCC applications. © 2013 S. Vidya et al.


Vidya S.,Electronic Materials Research Laboratory | Mathai K.C.,Electronic Materials Research Laboratory | Rejith P.P.,Electronic Materials Research Laboratory | Solomon S.,Dielectric Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Advances in Materials Science and Engineering | Year: 2013

The percolation behavior of superconductor-insulator composite, YBa 2Cu3O7-δ, and nano SmBa 2NbO2 synthesized by modified combustion technique was studied. Particle size of nano SmBa2NBO6 was determined using transmission electron microscopy. The chemical nonreactivity of nano SmBa2NbO6 with YBCO is evident from the X-Ray diffraction study which makes it a suitable nanoceramic substrate material for high temperature superconducting films. A systematic increase in the sintered density, approaching the optimum value of the insulating nanophase is clearly observed, as the vol.% of YBCO in the composite decreases. SEM micrograph showed uniform distribution of nanopowder among the large clusters of YBCO. The obtained percolation threshold is 26 vol% of YBCO in the composite. All the composites below the threshold value showed T C (0) 92 K even though the room resistivity increases with increase in vol.% of nano SmBa2NbO 6. The values of critical exponents obtained matches well with the theoretically expected ones for an ideal superconductor-insulator system. © 2013 S. Vidya et al.


Suresh M.K.,Electronic Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory | Sreemoolanadhan H.,Vikram Sarabhai Space Center | George C.N.,Bishop Moore College | And 4 more authors.
Materials Research Bulletin | Year: 2010

Nanocrystallinemagnesium titanate was synthesized through an auto-ignited combustion method. The phase purity of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder was in between 20 and 40 nm. The nanopowder could be sintered to 98% of the theoretical density at 1200 °C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant (ε r) of 16.7 and loss factor (tan δ) of the order of 10 -4 were obtained at 5 MHz when measured using LCR meter. The quality factor (Q u × f) 73,700 and temperature coefficient of resonant frequency (τ f) -44.3 ppm/°C, at 6.5 GHz are the best reported values for sintered pellets obtained from phase pure nanocrystalline MgTiO 3 powder. © 2010 Elsevier Ltd. All rights reserved.


Vidya S.,Electronic Materials Research Laboratory | Solomon S.,Dielectric Materials Research Laboratory | Thomas J.K.,Electronic Materials Research Laboratory
Journal of Electroceramics | Year: 2016

The synthesis of nanocrystalline Ba0.5Sr0.5MoO4 by an auto-igniting combustion technique is reported. The structural characterization done by X-ray diffraction, Fourier transform Raman spectroscopy and infrared spectroscopy reveals that the as-prepared powder itself is phase pure with tetragonal structure. The particle size determined from Transmission electron microscopy is 21 nm. The ultraviolet-visible absorption spectrum of the sample shows maximum absorption in the UV region and the optical band gap determined is 4.71 eV. The photoluminescence spectrum of Ba0.5Sr0.5MoO4 shows green emission, associated with the perfect order and crystallinity of the sample. The sample is sintered at a relatively low temperature of 815 °C. Scanning electron microscopy showed that the sample achieved 95 % of its theoretical density. The dielectric constant and loss factor of the sample measured at 5 MHz is found to be 10.58 and 1.66.×10−3 at room temperature. The effect of change in composition of A2+ site of scheelite AMO4 compounds comparative are also presented. The experimental results show that nano Ba0.5Sr0.5MoO4 is an excellent luminescent material and also a promising ‘Low temperature Co-fired Ceramic’. Also it is inferred that we can fine tune both optical and dielectric properties to desired values according to our requirements by adjusting the cationic stoichiometric ratio in [AO8] octahedron. © 2016 Springer Science+Business Media New York


Vidya S.,Electronic Materials Research Laboratory | Rejith P.P.,Electronic Materials Research Laboratory | John A.,Dielectric Materials Research Laboratory | Solomon S.,Dielectric Materials Research Laboratory | And 2 more authors.
Materials Research Bulletin | Year: 2011

A single step combustion process for the preparation of nanoparticles of yttrium barium stannous oxide is reported in this paper. The structure, phase purity and particulate properties of the as prepared nano YBa 2SnO 5.5 powder were examined by X-ray diffraction and transmission electron microscopy. The as prepared powder obtained itself is phase pure and possess cubic structure with lattice constant 8.240 Å. The particle size of the as prepared sample from Transmission Electron Microscopy analysis is in the range of ∼15 nm. Vibrational studies carried out on the as prepared powder also confirm the cubic structure of the as prepared sample. The thermal stability of the nano particle is analyzed by thermo gravimetric and differential thermal analysis. The material is a semiconductor with excellent luminescent properties. Chemical compatibility of the sample with YBCO is analyzed. The YBCO-YBa 2SnO 5.5 composite showed T c(0) at 92 K. © 2011 Elsevier Ltd. All rights reserved.

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