Properties of polycrystalline samples of Nd[sub 2[minus][ital x]]Ce[sub [ital x]]CuO[sub 4[minus][ital y]] obtained from a sol-gel precursor

Journal Article · Mon Nov 14 23:00:00 EST 1994 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.358050· OSTI ID:6716017

Barbeta, V B; Jardim, R F ^[1]; Ben-Dor, L ^[2]; Maple, M B ^[3]

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1. Instituto de Fisica, Universidade de Sao Paulo, CP20516, 01452-990, Sao Paulo, SP (Brazil)
2. Department of Inorganic and Analytical Chemistry, Hebrew University, Jerusalem 91904 (Israel)
3. Department of Physics and Institute for Pure and Applied Physical Sciences, UCSD, La Jolla, California 92093-0075 (United States)

Polycrystalline samples of Nd[sub 2[minus][ital x]]Ce[sub [ital x]]CuO[sub 4[minus][ital y]](0.0[le][ital x][le]0.17) obtained from a sol-gel precursor were sintered below the eutectic temperature and reduced under different conditions. From the results of x-ray powder diffraction, the tetragonal [ital T][prime] structure is preserved for Ce content up to [ital x]=0.17. A decrease in the lattice parameter [ital c] and a small increase in the lattice parameter [ital a] are observed with increasing Ce concentration. Electrical resistance [ital R]([ital T]) measurements performed on reduced samples with [ital x][ge]0.12 reveal superconducting behavior below [ital T][approx]25 K. We also found that all reduced samples display a striking double resistive superconducting transition and that the zero resistance state is achieved through two distinct drops in [ital R]([ital T]) at upper and lower transition temperatures [ital T][sub [ital ci]] and [ital T][sub [ital cj]]. The upper transition temperature [ital T][sub [ital ci]] has a maximum for Ce concentration [ital x]=0.14, which is independent of the reduction process. The lower transition temperature [ital T][sub [ital cj]] is observed in reduced samples with Ce content [ital x][ge]0.14 and decreases monotonically with increasing Ce concentration. Magnetic susceptibility measurements confirm bulk superconductivity in several reduced samples, and a significant diamagnetic contribution is only observed for temperatures below [ital T][sub [ital cj]]. The results are discussed within the framework of a granular superconductor model.

• OSTI ID: 6716017
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 76:10; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLYCRYSTALS
RARE EARTH COMPOUNDS
SCATTERING
SOL-GEL PROCESS
SUPERCONDUCTIVITY
TEMPERATURE RANGE
TEMPERATURE RANGE 0013-0065 K
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
X-RAY DIFFRACTION