rf surface resistance of a magnetically aligned sintered pellet of YBa sub 2 Cu sub 3 O sub 7

Journal Article · Thu Feb 15 00:00:00 EST 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345581· OSTI ID:6964488

Padamsee, H; Kirchgessner, J; Moffat, D; Rubin, D; Shu, Q S ^[1]; Hart, H R; Gaddipati, A R ^[2]

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1. Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (US)
2. GE Corporate Research and Development, Schenectady, New York 12301 (USA)

rf (radio frequency) properties of polycrystalline ceramic material are substantially inferior to those of the best microtwinned crystals. At 6 GHz and 77 K, the best surface resistance values for ceramics are {similar to}20 m{Omega}, compared to {lt}0.5 m{Omega} for high-quality crystals. The microwave resistance is observed to increase at higher rf fields for ceramics, e.g., two orders of magnitude between 0.1 and 10 Oe, but remains low for crystals. A possible reason for the inferior properties in randomly oriented polycrystalline ceramics is related to the anisotropy of the superconducting properties; crystals aligned unfavorably with the sampling rf field could be responsible for the high resistance. Another possibility is related to the difficulty of carrying current across the grain boundaries due to weak links arising from second phases, impurities, cracks, etc., at the boundaries. To elucidate the contribution from these two potential problem sources, we have measured the rf properties at 6 GHz of an oriented polycrystalline ceramic pellet prepared from a suspension of high purity powder in a 4-T magnetic field. Samples were characterized by x-ray diffraction, light microscopy, transmission electron microscopy, x-ray rocking curves, and x-ray pole figure studies, indicating a high degree of alignment, although not as complete as in epitaxial thin films. At liquid He temperature, the surface resistance is 28 times lower when the {ital c} axis is perpendicular to the plane in which rf currents flow than when the {ital c} axis is in the plane. At 77 K, the surface resistance is 3 m{Omega}, a significant improvement over the properties of the best randomly oriented material reported. At 4 K the resistance improves to 0.3 m{Omega}.

• OSTI ID: 6964488
• Journal Information: Journal of Applied Physics; (USA), Vol. 67:4; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
ELECTRICAL PROPERTIES
COPPER OXIDES
YTTRIUM OXIDES
ELECTRIC CONDUCTIVITY
GHZ RANGE 01-100
OPTICAL MICROSCOPY
ORIENTATION
POLYCRYSTALS
RADIOWAVE RADIATION
SUPERCONDUCTORS
SURFACES
TRANSMISSION ELECTRON MICROSCOPY
ULTRALOW TEMPERATURE
X-RAY DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
CRYSTALS
DIFFRACTION
ELECTROMAGNETIC RADIATION
ELECTRON MICROSCOPY
FREQUENCY RANGE
GHZ RANGE
MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties