Aditya Kumar; Bushra Khan; Gulab Singh; Manoj K. Singh; Upendra Kumar
Abstract
Single phase sample of CaSnO3 and Ca0.98Nd0.02Sn0.98Ti0.02O3 were synthesized by sol-gel route followed by calcination at 800 o C. The X-ray diffraction pattern of both samples showed monophasic, and their Rietveld refinement studies indicated that the samples belonged to orthorhombic crystal structure ...
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Single phase sample of CaSnO3 and Ca0.98Nd0.02Sn0.98Ti0.02O3 were synthesized by sol-gel route followed by calcination at 800 o C. The X-ray diffraction pattern of both samples showed monophasic, and their Rietveld refinement studies indicated that the samples belonged to orthorhombic crystal structure under space group Pbnm. Moreover, dopant substitution results in unit cell compression due to lower ionic radii of dopant than host. UV-Vis. spectroscopy study of samples reflected semiconducting samples. The direct optical band gap of doped sample found smaller (4.02 eV) than undoped (4.23 eV), due to formation of Nd 3+ state below conduction band. The dielectric constant of both samples (30 and 18) was found to be temperature independent up to 220 o C and 300 o C and tangent loss below 1 makes it suitable candidate for thermally stable capacitor application. Ac conductivity of samples was analyzed using Arrhenius model as a function of frequency and temperature, and the value of activation energy is reflected an electronic as well as mixed ionic and electronic conduction in samples. Based on these studies, the present material can be used in UV-filter, sensors, and mixed ionic and electronic conductor applications.
Divyanshu Bhatnagar; Ratnamala Chatterjee
Abstract
BaBiO3 (BBO) particles were successfully synthesized through solid-state route, to provide better understanding of its transport properties, which is not well studied yet. X-ray diffraction (XRD) measurement confirmed that the particles were crystallized with monoclinic structure in single phase. The ...
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BaBiO3 (BBO) particles were successfully synthesized through solid-state route, to provide better understanding of its transport properties, which is not well studied yet. X-ray diffraction (XRD) measurement confirmed that the particles were crystallized with monoclinic structure in single phase. The Raman spectrum of BBO sample revealed the existence of two different Bi sites (the octahedral BiO6/3 and the triangular pyramidal BiO4/2 cluster). Subsequently, the observation of low resolution and lattice scale imaging through high resolution transmission electron microscope (HRTEM) indicated the formation of monoclinic BBO particles of size ~ 50-60 nm. The ring pattern obtained from selected area electron diffraction (SAED) inveterate polycrystalline nature of the sample and calculated structural parameters well harmonized with XRD results. As expected, BBO showed semiconducting behavior with resistivity of ~ 3.8 kΩ-cm at room temperature along with an excellent NTC (negative temperature coefficient) thermistor characteristic. The dielectric measurements and impedance spectroscopy studies reveal that BBO exhibit two typical characteristics, i.e., diffuse phase transition and frequency dependent dielectric maxima, of relaxor oxides; with negative dielectric constant above 550 K.
Kuldeep Chand Verma; R.K. Kotnala
Abstract
We reported the Core/Shell structures of CoFe2-xCexO4 (CFCeO) nanoparticles were prepared by a chemical combustion method. The Rietveld refinement of X-ray diffraction pattern results into CoFe2O4 spinel structure and thevariation in lattice parameters have been found with doping of Ce ions. Transmission ...
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We reported the Core/Shell structures of CoFe2-xCexO4 (CFCeO) nanoparticles were prepared by a chemical combustion method. The Rietveld refinement of X-ray diffraction pattern results into CoFe2O4 spinel structure and thevariation in lattice parameters have been found with doping of Ce ions. Transmission Electron Microscopy analysis has shown Core/Shell type nanoparticles. The stoichiometric composition of Co, Fe, Ce and O atoms has been analyzed through X-ray fluorescence elemental detection. Fourier transform infrared spectra could detect organic extent, tetrahedral (Fe-O), octahedral (Fe(Ce)-O-Co) and lattice disorder in CFO nanoparticles with Ce doping. Defects related oxygen vacancies are analyzed in Photoluminescence emission spectra. The room temperature magnetic measurement of CFO nanoparticles is highly influenced with Ce ions. The magnetic interactions are antiferromagnetic at room temperature that confirmed by zero field cooling and field cooling magnetic measurements at 100 Oe. However, the spin glass and ferromagnetic clustered growth may also exist in CFCeO samples that reduce room temperature ferromagnetism. The dielectric measurement indicates polarization up to higher frequency region that enhanced with Ce ions.