Browsing by Author "Giapintzakis, John"
Now showing items 21-40 of 149
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Conference Object
Direct observation of microscopic inhomogeneities in high-Tc superconductors using energy-dispersive diffraction of synchrotron-produced xrays
Skelton, Earl F.; Qadri, Syen B.; Osofsky, Michael S.; Drews, A. R.; Broussard, P. R.; Hu, J. Z.; Finger, L. W.; Vanderah, Terrell A.; Kaiser, D.; Peng, J. L.; Anlage, Steven M.; Greene, Richard L.; Giapintzakis, John (Affiliation: Naval Research Lab., Washington, DC,, USA, United StatesCorrespondence Address: Skelton, Earl F.Naval Research Lab., Washington, DC,, USAUnited States, 1995)Evidence of micron-sized structural inhomogeneities in several high transition temperature (T c) superconductors is presented. By illuminating samples with high energy, highly collimated x rays produced on a synchrotron ...
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Article
Disorder-induced vortex phase transition in untwinned YBa2Cu3O7-δ crystal
Giller, D.; Giapintzakis, John; Shaulov, A.; Yeshurun, Y. (2000)Local magnetic measurements in an untwinned YBa2Cu3O7-δ crystal as a function of temperature, field and time reveal anomalies occurring along the same line BSS(T) in the field-temperature plane. We identify BSS(T) as a ...
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Article
Editorial
Dinescu, Maria; D’Addato, Sergio; Giapintzakis, John; Wójcik, Marek (2017)
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Article
Effect of antimony-doping and germanium on the highly efficient thermoelectric Si-rich-Mg2(Si,Sn,Ge) materials
Vlachos, N.; Polymeris, G. S.; Manoli, M.; Hatzikraniotis, E.; Khan, A. U.; Lioutas, C. B.; Stefanaki, E. C.; Pavlidou, E.; Paraskevopoulos, K. M.; Giapintzakis, John; Kyratsi, Theodora (2017)Two series of materials (a) Mg2Si0.55-ySn0.4Ge0.05Sby, 0 ≤ y ≤ 0.0175 and (b) Mg2Si0.5875-xSn0.4GexSb0.0125, 0 ≤ x ≤ 0.20 have been developed and studied in terms of structural features and thermoelectric properties/performance. ...
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Article
The effect of correlated and point defects on the vortex lattice melting transition in single-crystal YBa2Cu3O7-δ
Kwok, W. K.; Fendrich, J.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G. W.; Giapintzakis, John (1994)The vortex melting transition Tm in several untwinned and twinned crystals is measured resistively in fields up to 8T. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the ...
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Article
The Effect of Ge on Mg2Si0.6−x Sn0.4Ge x Materials
Vlachos, N.; Hatzikraniotis, E.; Mihailescu, C. N.; Giapintzakis, John; Kyratsi, Theodora (2014)In this work, we investigate the influence of the introduction of Ge on the thermoelectric properties of Bi-doped quaternary Mg2Si0.6−x Sn0.4Ge x alloys. Mg2Si0.58−x Sn0.4Bi0.02Ge x materials were fabricated by a low ...
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Article
Effect of gold and silver nanoislands on the electrochemical properties of carbon nanofoam
Spanakis, E.; Pervolaraki, M.; Giapintzakis, John; Katsarakis, N.; Koudoumas, E.; Vernardou, D. (2013)•Metallic nanoislands coated on the exterior surface of carbon nanofoam.•Their properties are dependent on the type of the metallic nanoisland.•The gold-associated redox reactions enhance their electrochemical performance.
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Article
Effect of inhomogeneities on the fluctuation-induced cusp in the specific heat of high temperature superconductors
Sharifi, F.; Giapintzakis, John; Ginsberg, D. M.; Harlingen, D. J. Van (1989)We consider the effect of inhomogeneities on the electronic specific heat in high temperature superconductors. We find that a modest spread in the transition temperature of the sample can significantly alter the detailed ...
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Effect of microstructure on the thermoelectric performance of La1−xSrxCoO3
Viskadourakis, Z.; Athanasopoulos, G. I.; Kasotakis, E.; Giapintzakis, John (2016)We present a case where the microstructure has a profound effect on the thermoelectric properties of oxide compounds. Specifically, we have investigated the effect of different sintering treatments on La1−xSrxCoO3 samples ...
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Article
Effect of silicon nitride/oxide on the structure and the thermal conductivity of CoSi nanocomposites
Ioannou, M.; Delimitis, A.; Symeou, E.; Giapintzakis, John; Kyratsi, Theodora (2017)In this work, the fabrication of nanocomposites with silicon nitride/oxide into the thermoelectric matrix of cobalt silicide is presented. The different concentrations of nano-Si3N4 were intentionally introduced by mechanical ...
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Article
Effect of vacancy doping on the Haldane spin-liquid state in PbNi2-xMgxV2O8
Zorko, A.; Arčon, D.; Lappas, A.; Giapintzakis, John; Saylor, C.; Brunel, L. C. (2002)The effect of spin-vacancy doping on the ground state of the quasi-one-dimensional S=1 quantum antiferromagnet PbNi2V2O8 is studied by X band as well as high-field ESR. A very broad ESR line is observed at low temperatures ...
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Article
Electrical, structural, and optical properties of sulfurized Sn-doped In2O3 nanowires
Zervos, Matthew; Mihailescu, C. N.; Giapintzakis, John; Othonos, A.; Travlos, A.; Luculescu, C. R. (2015)Sn-doped In2O3 nanowires have been grown on Si via the vapor-liquid-solid mechanism at 800 °C and then exposed to H2S between 300 to 600 °C. We observe the existence of cubic bixbyite In2O3 and hexagonal SnS2 after processing ...
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Conference Object
Electron microscopy study of thermoelectric (BixSb1-x)2Te3thin film
Breza, A.; Lioutas, C. B.; Giapintzakis, John (Springer Science and Business Media, LLC, 2015)In the present work, transmission electron microscopy (TEM) techniques were used in order to study the morphology and investigate the structural properties of a (BixSb1-x)2Te3(BST) thin film. The sample was fabricated on ...
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Article
Enhanced thermoelectric properties in vacuum-annealed Bi0.5Sb1.5Te3 thin films fabricated using pulsed laser deposition
Symeou, E.; Nicolaou, Ch.; Kyratsi, Theodora; Giapintzakis, John (2019)Localized cooling in microelectronics and nanoelectronics as well as energy autonomy in applications such as wireless sensor networks and wearable electronics could be well served by thin-film thermoelectric devices ...
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Enhancing the nanoscratch resistance of pulsed laser deposited DLC films through molybdenum-doping
Constantinou, M.; Pervolaraki, M.; Koutsokeras, L.; Prouskas, C.; Patsalas, P.; Kelires, P.; Giapintzakis, John; Constantinides, G. (2017)Pulsed laser deposition was used to grow DLC and molybdenum-doped DLC (DLC:Mo) films, with metal contents up to 3.2 at.%, on silicon substrates. The microstructural details of the films were investigated using X-ray ...
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Evidence for dx2-y2 pairing from the magnetic field modulation of YBa2Cu3O7-Pb Josephson junctions
Wollman, D. A.; Harlingen, D. J. Van; Giapintzakis, John; Ginsberg, D. M. (1995)We have measured the magnetic field modulation of the critical current of YBCO-Au-Pb Josephson junctions fabricated on the a and b edges and straddling the a-b corners of YBCO single crystals. In corner junctions, the ...
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Article
Evidence of order-parameter symmetry and of a normal metallic state in electron-irradiated YBa2Cu3O7-8 (YBCO)
Ginsberg, D. M.; Giapintzakis, John; Kirk, M. A. (1996)A key difference between a d-wave superconductor and an anisotropic s-wave one is the expected effect of nonmagnetic point defects on Tc. For the former, Tc becomes zero, whereas for the latter, Tc reaches a nonzero constant ...
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Experimental determination of the absolute temperature modulation in photothermal microscopy of Y1Ba2Cu3O7 crystals
Studenmund, W. R.; Fishman, I. M.; Kino, G. S.; Giapintzakis, John (1997)We present a technique to experimentally determine the value of the temperature perturbation ST in photothermal microscopy. Knowledge of δT is necessary for proper analysis of the differential optical reflectivity (∂R/∂T) ...
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Experimental evidence for a multicritical point in the magnetic phase diagram for the mixed state of clean untwinned YBa2Cu3O7
Safar, H.; Gammel, P. L.; Huse, D. A.; Bishop, D. J.; Lee, W. C.; Giapintzakis, John; Ginsberg, D. M. (1993)We report on transport measurements in fields up to 16 T in clean, untwinned single crystals of YBa2Cu3O7 which indicate that there is a critical end point for first-order melting in the H-T phase diagram in the mixed state ...
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Ferromagnetic and antiferromagnetic interactions in lanthanum cobalt oxide at low temperatures
Androulakis, J.; Katsarakis, N.; Giapintzakis, John (2001)Systematic dc and ac magnetic susceptibility studies have been performed on single-phase (formula presented) powder samples. Evidence is presented in support of the existence of ferromagnetic (FM1, FM2) and antiferromagnetic ...