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S. R. Shannigrahi R. N. P. Choudhary H. N. Acharya T. P. Sinha 《Journal of Materials Science》2000,35(7):1737-1742
Potassium-modified PLZT [Pb0.92(La1 – zKz)0.08(Zr0.60Ti0.40)0.98 + 0.04zO3 (z = 0.0, 0.1, 0.3, 0.5, 0.7)] ceramics were synthesised using sol-gel technique. Preliminary structural and microstructural parameters were determined using XRD, SEM and TEM techniques. Detailed studies of dielectric properties at 10 kHz in a wide temperature range suggest that the compounds have diffuse phase transition of second order. Studies of spontaneous polarisation, pyroelectric and piezoelectric properties yielded data for devices. 相似文献
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Natwar Modani Seema Nagar Saswata Shannigrahi Ritesh Gupta Kuntal Dey Saurabh Goyal Amit A. Nanavati 《World Wide Web》2014,17(5):899-919
Community detection in social networks is a well-studied problem. A community in social network is commonly defined as a group of people whose interactions within the group are more than outside the group. It is believed that people’s behavior can be linked to the behavior of their social neighborhood. While shared characteristics of communities have been used to validate the communities found, to the best of authors’ knowledge, it is not demonstrated in the literature that communities found using social interaction data are like-minded, i.e., they behave similarly in terms of their interest in items (e.g., movie, products). In this paper, we experimentally demonstrate, on a social networking movie rating dataset, that people who are interested in an item are socially better connected than the overall graph. Motivated by this fact, we propose a method for finding communities wherein like-mindedness is an explicit objective. We find small tight groups with many shared interests using a frequent item set mining approach and use these as building blocks for the core of these like-minded communities. We show that these communities have higher similarity in their interests compared to communities found using only the interaction information. We also compare our method against a baseline where the weight of edges are defined based on similarity in interests between nodes and show that our approach achieves far higher level of like-mindedness amongst the communities compared to this baseline as well. 相似文献
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Binita Ghosh Alo Dutta Santiranjan Shannigrahi T. P. Sinha 《Journal of Materials Science》2014,49(2):819-826
The electronic structure and the vibrational property of the double perovskite oxide, Ca2GdTaO6 (CGT), synthesized by solid-state reaction technique are investigated. Density functional theory calculations performed by the VASP show a direct band gap energy of 3.2 eV. The calculated density of states (DOS) has been compared to the valence band spectrum measured by X-ray photoelectron spectroscopy (XPS). The calculated electronic structures of CGT are qualitatively similar to those of the XPS spectra in terms of spectral features and relative intensities. The DOS of CGT shows that the Gd f, Ta d and O 2p states are hybridized. The band-structure calculation is used to obtain the optical dielectric constant of the sample. The inter-band contributions to the optical properties of CGT have been analysed. Raman spectrum of the sample taken at 488 nm excitation wavelength shows five primary strong peaks at 112, 215, 320, 458 and 767 cm?1. Lorentzian lines with 17 bands have been used to fit the Raman spectrum. The eigen frequencies of different phonon modes have been theoretically calculated. The calculated results are compared with the experimental data. 相似文献
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The polycrystalline samples of dysprosium (Dy)-modified bismuth ferrite (i.e., Bi1−xDyxFeO3; x=0–0.2 with the interval of 0.05) (BDFO) were synthesized using a high-temperature solid-state reaction method. Preliminary X-ray structural analysis showed that the reported crystal structure of BiFeO3 (rhombohedral) is invariant even with Dy-substitution at the Bi-site upto x=0.2. The scanning electron micrograph of the compounds showed (i) the uniform distribution of grains on the sample surface with high density and (ii) reduction of grain size on increasing Dy content in BiFeO3 (BFO). Studies of impedance, electrical modulus and electric conductivity of the materials in wide frequency (10–1000 kHz) and temperature (30–500 °C) ranges using a complex impedance spectroscopy technique have provided new and interesting information on the contribution of grains, grain boundary and interface in these parameters. Detailed studies of impedance spectroscopy clearly exhibit the dielectric relaxation of non-Debye type. The ac conductivity of the Dy-substituted BFO obeyed Jonscher's universal power law. An increase in Dy-content in BDFO results in the increase of spontaneous magnetization of BFO due to the collapse of spin cycloid structure. 相似文献
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Multiferroic epitaxial films, include SrRuO3/Pb(Zr0.95Ti0.05)O3/CoFe2O4 has been successfully deposited on SrTiO3 substrate by pulsed-laser deposition technique. The results show that the prepared films exhibit a single phase. The Pb(Zr0.95Ti0.05)O3 (PZT) film was highly textured with (1 0 0) orientation and gives good ferroelectric properties with saturated polarization of 15 μC/cm2. The magnetic coercivity of CoFe2O4 film on Pb(Zr0.95Ti0.05)O3 has been dampened to 0.9 kOe. The anisotropic magnetically behavior of CoFe2O4 film was changed to isotropic by using high Zr concentrated PZT as underneath layer. Heterostructure films show a good ferromagnetic and ferroelectric coupling that lead to the large magnetoelectricity of 287 mV/cm Oe. 相似文献
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Polycrystalline samples of (Pb1-zLaz)(Zr0.60Ti0.40)1-z/4O3 (where z = 0.00, 0.05, 0.09, 0.12, 0.14 mol %) (abbreviated as PLZT) were synthesized through acetate-alkoxide sol-gel route. The formation and existence of different crystallographic phases as a function of z was checked through X-ray, TEM, SEM and dielectric studies. The diffuse phase transition (DPT) was observed in PLZT with higher concentration of La (i.e., for z = 0.00 to 0.12), but for z = 0.14, the compound did not show any phase transition. 相似文献
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A. HuangS.R. Shannigrahi 《Thin solid films》2011,519(15):4793-4797
Lead-free polycrystalline BiFeO3 (BFO) thin films were developed using a chemical solution deposition method to deposit the films and the multi-mode 2.45 GHz microwave furnace to optimize the annealing condition of the films. Phase-pure BFO films were obtained at 500 °C-600 °C for 1-5 min with a heating rate of 10 °C/min. The film by microwave annealing (MW) at 550 °C for 5 min exhibited a (012)-preferred orientation with a dense morphology of grain size ~ 294 nm. Its dielectric constant of 96.2, low leakage current density of 2.466 × 10− 6 A/cm2, polarization (2Pr) and coercive field (2Ec) of 0.931 μC/cm2 and 57.37 kV/cm, respectively, were improved compared to those by conventional annealing (CA) at the same annealing conditions. 相似文献
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Santiranjan R. Shannigrahi Sun-Hwa Lee Hyun M. Jang 《Journal of the American Ceramic Society》2002,85(8):2122-2124
Pb0.98 (La1− x Li x )0.02 (Zr0.55 Ti0.45 )O3 (PLLZT with 0.1 ≤ x ≤ 0.7) thin films were sol-gel-grown on Pt(111)/Ti/SiO2 /Si substrates, employing a thin lead zirconate titanate (PZT) template layer. Films annealed at >550°C showed a highly (111)-oriented preferential growth. Typical values of the switchable remanent polarization (2 P r ) and the coercive field ( E c ) of the PLLZT/PZT/Pt film capacitor for x = 0.3 were 50 μC/cm2 and 39 kV/cm, respectively, at 5 V. All the PLLZT/PZT/Pt capacitors (for 0.1 ≤ x ≤ 0.7) exhibited fatigue-free behavior up to 6.5 × 1010 switching cycles, a quite stable charge retention profile with time, and high 2 P r values, all which assure their suitability for nonvolatile ferroelectric memories. 相似文献