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Your search keyword '"Arendt, P. N."' showing total 175 results
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175 results on '"Arendt, P. N."'

1. Angular dependent vortex pinning mechanisms in YBCO coated conductors and thin films

Author

Civale, L., Maiorov, B., Serquis, A., Willis, J. O., Coulter, J. Y., Wang, H., Jia, Q. X., Arendt, P. N., MacManus-Driscoll, J. L., Maley, M. P., and Foltyn, S. R.

Subjects
Condensed Matter - Superconductivity
Abstract

We present a comparative study of the angular dependent critical current density in YBa2Cu3O7 films deposited on IBAD MgO and on single crystal MgO and SrTiO3 substrates. We identify three angular regimes where pinning is dominated by different types of correlated and uncorrelated defects. We show that those regimes are present in all cases, indicating that the pinning mechanisms are the same, but their extension and characteristics are sample dependent, reflecting the quantitative differences in texture and defect density. In particular, the more defective nature of the films on IBAD turns into an advantage as it results in stronger vortex pinning, demonstrating that the critical current density of the films on single crystals is not an upper limit for the performance of the IBAD coated conductors., Comment: 14 pages, 3 figures. Submitted to APL

Published
2003
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2. Through-thickness superconducting and normal-state transport properties revealed by thinning of thick film ex situ YBa2Cu3O7-x coated conductors

Author

Feldmann, D. M., Larbalestier, D. C., Feenstra, R., Gapud, A. A., Budai, J. D., Holesinger, T. G., and Arendt, P. N.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Materials Science
Abstract

A rapid decrease in the critical current density (Jc) of YBa2Cu3O7-x (YBCO) films with increasing film thickness has been observed for multiple YBCO growth processes. While such behavior is predicted from 2D collective pinning models under certain assumptions, empirical observations of the thickness dependence of Jc are believed to be largely processing dependent at present. To investigate this behavior in ex situ YBCO films, 2.0 and 2.9 um thick YBCO films on ion beam assisted deposition (IBAD) - yttria stabilized zirconia (YSZ) substrates were thinned and repeatedly measured for rho(T) and Jc(H). The 2.9 um film exhibited a constant Jc(77K,SF) through thickness of ~1 MA/cm2 while the 2.0 um film exhibited an increase in Jc(77K,SF) as it was thinned. Neither film offered evidence of significant dead layers, suggesting that further increases in critical current can be obtained by growing thicker YBCO layers., Comment: To appear in Applied Physics Letters

Published
2003
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24. Microstructure and transport properties of Y-rich YBa2Cu3O7-δ thin films.

Author

Wang, H., Serquis, A., Maiorov, B., Civale, L., Jia, Q. X., Arendt, P. N., Foltyn, S. R., MacManus-Driscoll, J. L., and Zhang, X.

Subjects
THIN films, YTTRIUM alloys, MICROSTRUCTURE, BORON compounds, POLYCRYSTALS, STRONTIUM compounds, TITANIUM dioxide
Abstract

Epitaxial YXBa2Cu3O7-δ (YXBCO) thin films were deposited by pulsed laser deposition on both single crystal SrTiO3 (100) and buffered polycrystalline metal substrates, where X=0.9, 1.0, 1.1, 1.2, and 1.3. The self-field critical current density (Jc) of YXBCO exhibits the best performance at X=1.1 for the samples on both single crystal substrates and metal substrates. Epitaxial Y2O3 nanoparticles were observed in Y-rich samples (X>1.0) by X-ray diffraction and cross-sectional transmission electron microscopy. The field-dependence and angular-dependence measurements show that Y2O3 nanoparticles improve the in-field Jc performance, especially in the low field regime, without reducing self-field Jc of YBCO films. [ABSTRACT FROM AUTHOR]

Published
2006
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25. Reflection high-energy electron diffraction experimental analysis of polycrystalline MgO films with grain size and orientation distributions.

Author

Brewer, R. T., Atwater, Harry A., Groves, J. R., and Arendt, P. N.

Subjects
MAGNESIUM, ION bombardment, HIGH energy electron diffraction
Abstract

Analysis of biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) has been performed using a quantitative reflection high-energy electron diffraction (RHEED) based method. MgO biaxial texture is determined by analysis of diffraction spot shapes from single RHEED images, and by measuring the width of RHEED in-plane rocking curves for MgO films grown on amorphous Si[sub 3]N[sub 4] by IBAD using 750 eV Ar[sup +] ions, at 45° incidence angle, and MgO e-beam evaporation. RHEED-based biaxial texture measurement accuracy is verified by comparison with in-plane and out-of-plane orientation distribution measurements made using transmission electron microscopy and x-ray rocking curves. In situ RHEED measurements also enable the analysis of the evolution of the biaxial texture which narrows with increasing film thickness. RHEED-based measurements of IBAD MgO biaxial texture show that the minimum in-plane orientation distribution depends on the out-of-plane orientation distribution, and indicates that the minimum obtainable in-plane orientation on distribution is 2°. [ABSTRACT FROM AUTHOR]

Published
2003
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26. Characterization of the Structure of Y-Ba-Cu-O Coated Conductors

Author

Foltyn, S. R., Kung, H. H., Foltyn S. R., Arendt P. N., Maley, Maley, M. P., and Arendt, P. N.

Abstract

Transmission electron microscopy (TEM) has been applied to the microstructural investigation of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) thick films deposited on polycrystalline Ni-based metal substrates by pulsed laser deposition. The films were found to be strongly textured with c-axis oriented grains aligned perpendicular to the substrates. Despite the large average in-plane misorientation, as was estimated from selected area electron diffraction and x-ray diffraction, TEM inspection reveals colonies of submicron-sized grains with low angle tilt grain boundaries. The linkage of the colony structures may provide a continuous percolation pathway for the supercurrent transport in YBCO, which may provide the mechanism for the higher than expected critical current density J{sub c}. Periodic arrays of grain boundary dislocations were observed, which may serve as effective flux pinners.

Published
1999

27. Microwave surface resistance of YBa2Cu3O7 thin films on LaAlO3 substrates.

Author

Cooke, D. W., Gray, E. R., Arendt, P. N., Elliott, N. E., Rollett, A. D., Schofield, T. G., Mogro-Campero, A., and Turner, L. G.

Subjects
COPPER oxide superconductors, ELECTRIC resistance, THIN films
Abstract

Presents a study that measured the microwave surface resistance of yttrium-barium-copper-oxide thin film superconductors on lanthanum aluminum oxide substrates. Methodology; Correlation between the critical current density and the temperature of the thin films; Determination of the metal stoichiometry of the thin films.

Published
1990
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28. Growth Optimization of YBa2NbO6 Buffer Layers (Postprint)

Author

AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIR/POWER DIV/MECHANICAL ENERGY CONVERSION BRANCH, Yust, N A, Haugan, T J, Tolliver, J C, Barnes, P N, Sathiraju, S, Nekkanti, R N, Maartense, I, Campbell, T L , A L, Jia, Q X, Arendt, P N, AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIR/POWER DIV/MECHANICAL ENERGY CONVERSION BRANCH, Yust, N A, Haugan, T J, Tolliver, J C, Barnes, P N, Sathiraju, S, Nekkanti, R N, Maartense, I, Campbell, T L , A L, Jia, Q X, and Arendt, P N

Abstract

The growth optimization of YBa2NbO6 (YBNO) buffer layers on LaAlO3 (100), MgO (100) single crystals, and IBAD MgO buffered Inconel substrates has been investigated. X-ray diffraction confirms the epitaxial growth of highly h00 oriented YBNO thin films on single crystal substrates and IBAD MgO buffered Inconel substrates. The best average surface roughness of the YBNO films deposited on buffered substrates is 2 nm. The critical temperature (Tc) of YBa2Cu3O7-x (Y-123) thin films deposited on these YBNO buffer layers ranges from 80 to 87 K. The deposition of YBNO may be further optimized and the IBAD MgO layers were only of sufficient quality to test for compatibility and epitaxial growth of the new buffer. Hence, the results presented here are preliminary in nature and can be improved upon., Conference paper published in the proceedings of the Materials Research Society Symposium, Vol. EXS-3, 2004.

Published
2012

29. High-T/sub c/ coated conductors-performance of meter-long YBCO/IBAD flexible tapes

Author

Foltyn, S. R., Arendt, P. N., Dowden, P. C., DePaula, R. F., Groves, J. R., Coulter, J. Y., Quanxi Jia, Maley, M. P., and Peterson, D. E.

Abstract

One meter long tapes based on 50-100 /spl mu/m thick by 1 cm wide nickel alloy substrates have been coated in a continuous process with a textured yttria-stabilized zirconia layer by ion beam-assisted deposition, followed by a 1-2 /spl mu/m thick layer of YBCO by pulsed laser deposition. The best result to date is a tape with a critical current (I/sub c/) at 75 K of 96 A over an 87 cm measurement length. The overall critical current density and engineering current density are 1 MA/cm/sup 2/ and 10 kA/cm/sup 2/, respectively. Using a special probe, individual I-V curves were generated for each centimeter of tape length in order to investigate longitudinal uniformity of the transport properties: the highest and lowest I/sub c/ values fall within a range of /spl plusmn/25%.

Published
1999

30. The Shape of Pulsar Polar Caps

Author

Arendt, P. N. and Eilek, J. A.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences
Abstract

Rotation distorts the vacuum magnetic field of a pulsar from that of a simple dipole. The effect is particularly strong close to the light cylinder, but also affects the field close to the stellar surface. We find the shape and locus of the field lines which just close at the light cylinder. Their footpoints define the pulsar polar cap. We find this cap is asymmetric and distorted. We also find that the polar cap is not strongly elliptical. This result disagrees with calculations based on the non-rotating dipole field. We present our numerical results, and discuss consequences for interpretation of mean profiles and for pulsar statistics., 14 pages, 14 figures. Uses AASTeX macros v. 4.0, and psfig.sty for figure inclusion. Submitted to the Astrophysical Journal

Published
1998
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31. Reflection High-Energy Electron Diffraction Experimental Analysis of Polycrystalline MgO Films with Grain Size and Orientation Distributions

Author

CALIFORNIA INST OF TECH PASADENA T J WATSON LABS OF APPLIED PHYSICS, Brewer, R T, Atwater, Harry A, Groves, J R, Arendt, P N, CALIFORNIA INST OF TECH PASADENA T J WATSON LABS OF APPLIED PHYSICS, Brewer, R T, Atwater, Harry A, Groves, J R, and Arendt, P N

Abstract

Analysis of biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) has been performed using a quantitative reflection high-energy electron diffraction (RHEED) based method. MgO biaxial texture is determined by analysis of diffraction spot shapes from single RHEED images, and by measuring the width of RHEED in-plane rocking curves for MgO films grown on amorphous Si3N4 by IBAD using 750 eV Ar+ ions, at 45 incidence angle, and MgO e-beam evaporation. RHEED-based biaxial texture measurement accuracy is verified by comparison with in-plane and out-of-plane orientation distribution measurements made using transmission electron microscopy and x-ray rocking curves. In situ RHEED measurements also enable the analysis of the evolution of the biaxial texture which narrows with increasing film thickness. RHEED-based measurements of IBAD MgO biaxial texture show that the minimum in-plane orientation distribution depends on the out-of-plane orientation distribution, and indicates that the minimum obtainable in-plane orientation on distribution is 2 ., Published in the Journal of Applied Physics, v93 n1 p205-210, 1 Jan 2003. Sponsored in part by DARPA. Prepared in collaboration with the Superconductor Technology Center, Los Alamos National Laboratories, Los Alamos, NM.

Published
2003

32. Ultrastrong, Stiff, and Lightweight Carbon-Nanotube Fibers

Author

Zhang, X., primary, Li, Q., additional, Holesinger, T. G., additional, Arendt, P. N., additional, Huang, J., additional, Kirven, P. D., additional, Clapp, T. G., additional, DePaula, R. F., additional, Liao, X., additional, Zhao, Y., additional, Zheng, L., additional, Peterson, D. E., additional, and Zhu, Y., additional

Published
2007
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33. Structure‐Dependent Electrical Properties of Carbon Nanotube Fibers

Author

Li, Q. W., primary, Li, Y., additional, Zhang, X. F., additional, Chikkannanavar, S. B., additional, Zhao, Y. H., additional, Dangelewicz, A. M., additional, Zheng, L. X., additional, Doorn, S. K., additional, Jia, Q. X., additional, Peterson, D. E., additional, Arendt, P. N., additional, and Zhu, Y. T., additional

Published
2007
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50. Dual Ion Assist Beam Deposition of Magnesium Oxide for Coated Conductors.

Author

Groves, J. R., Arendt, P. N., Holesinger, T. G., Hammond, R. H., Foltyn, S. R., DePaula, R. F., Stan, L., and Usov, I. O.

Subjects
*IONS, *PROPERTIES of matter, *ION bombardment, *MAGNESIUM compounds, *X-ray diffraction, *HIGH temperature superconductors, *HIGH temperature superconductivity
Abstract

Ion Beam Assisted Deposition (IBAD) of Magnesium Oxide (MgO) has been proven to be a viable route for producing template films used to deposit high quality YBCO coated conductors on flexible polycrystalline metal substrates. Here we will discuss improvements in this process using a dual ion assist beam configuration. Dual ion assist beam deposition of MgO reduces the requirements for substrate surface finishing while maintaining comparable film quality (phi scan full-width at half-maximum values between 7 and 8 degrees). Furthermore, this adaptation of the IBAD process eliminates the degradation of MgO texture observed in thick IBAD MgO films deposited on silicon nitride. We have deposited films up to 50 nanometers thick without degradation of in-plane texture. Increasing the MgO thickness increases the chemical stability of the template layer and can eliminate the necessity for subsequent buffer layers or the application of the homoepitaxial MgO layer needed to stabilize the thin, conventional IBAD MgO layer. Initial results of subsequently deposited YBCO on these dual assist ion beam MgO templates are quite promising. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2006
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