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Surjith A.,Microwave Materials Group | James N.K.,Microwave Materials Group | Ratheesh R.,Microwave Materials Group
Journal of Alloys and Compounds | Year: 2011

Low dielectric ceramics in the Al2W3-xMo xO12 (x = 0-3) system have been prepared through solid state ceramic route. The phase purity of the ceramic compositions has been studied using powder X-ray diffraction (XRD) studies. The microstructure of the sintered ceramics was evaluated by Scanning Electron Microscopy (SEM). The crystal structure of the ceramic compositions as a result of Mo substitution has been studied using Laser Raman spectroscopy. The microwave dielectric properties of the ceramics were studied by Hakki and Coleman post resonator and cavity perturbation techniques. Al2MoxW 3-xO12 (x = 0-3) ceramics exhibited low dielectric constant and relatively high unloaded quality factor. The temperature coefficient of resonant frequency of the compositions is found to be in the range -41 to -72 ppm/°C. © 2011 Elsevier B.V. Source


Neelakantan U.A.,Microwave Materials Group | Kalathil S.E.,Microwave Materials Group | Ratheesh R.,Microwave Materials Group
European Journal of Inorganic Chemistry | Year: 2015

A new ultralow-temperature-sinterable BaV2O6 ceramic was prepared through a conventional solid-state ceramic method. Thermogravimetric and differential-scanning-calorimetry analyses were performed to confirm the phase formation of BaV2O6. Phase purity and crystal structure of the ceramic material were studied by using X-ray diffraction analysis and Raman spectroscopic studies. BaV2O6 crystallizes in an orthorhombic unit cell, and the calculated lattice parameters are a = 8.532 A˚, b = 12.583 A˚, and c = 7.554 A˚. BaV2O6 ceramic was well sintered at 550°C for 1 h and exhibited a dense microstructure with excellent microwave properties, for example, a dielectric constant of 11.2, a Qxf value of 42790 GHz, and a temperature coefficient of resonant frequency of 28.2 ppm/°C. The BaV2O6 ceramic exhibits a linear coefficient of thermal expansion of 10 ppm/°C in the range 30-350°C. The BaV2O6 ceramic shows good chemical compatibility with Al electrodes, which makes it as a suitable candidate material for ULTCC technology. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA. Source

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