Moessbauer study of Fe site occupancy and its effect on Tc in YBa sub 2 (Cu sub 1 minus x Fe sub x ) sub 3 O sub 6+ y as a function of thermal treatments

Journal Article · Sat Sep 01 00:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.42.4202· OSTI ID:6482598

Smith, M G ^[1]; Taylor, R D ^[2]; Oesterreicher, H ^[3]

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1. Physics Division, Los Alamos National Laboratory, Los Alamos, NM (USA) Department of Chemistry, B-017, University of California, San Diego, La Jolla, CA (USA)
2. Physics Division, Los Alamos National Laboratory, Los Alamos, NM (USA)
3. Department of Chemistry, B-017, University of California, San Diego, La Jolla, CA (USA)

Synthesis of YBa{sub 2}(Cu{sub 1{minus}{ital x}}Fe{sub {ital x}}){sub 3}O{sub 6+{ital y}} ({ital x}=0.06, 0.10) under relatively reducing conditions (inert atmosphere) and subsequent careful low-temperature annealing in O{sub 2} should produce materials with a lower ratio ({ital r}) of Fe in the Cu(1) versus the Cu(2) site compared with conventionally prepared materials. This is expected due to the higher oxygen coordination of 5 in the Cu(2) site (denoted (2)5) under these conditions and is here confirmed by Moessbauer-effect measurements. These low-{ital r} materials crystallize in the orthorhombic structure and exhibit an increased superconducting transition temperature {Tc} compared with conventionally prepared ones. We assume that in conventionally prepared materials Fe at the Cu(1) site is surrounded by clusters of excess O that maintain tetragonal structures and localize charge and depress {Tc}. The reversal to orthorhombic structure is explained as a result of an increase of Fe in Cu(2) and of oxygen-starvation--Fe clusters in the Cu(1) site (sharing O) due to synthesis involving low-O fugacity at relatively low temperatures. This leaves the rest of the Cu(1) sites in an orthorhombic environment. The increase of Fe occupancy on Cu(2) indicates that Fe on Cu(2) is not detrimental to superconductivity and may actually play a role in charge fluctuations.

• OSTI ID: 6482598
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 42:7; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
ANNEALING
BARIUM COMPOUNDS
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FLUCTUATIONS
HEAT TREATMENTS
HIGH-TC SUPERCONDUCTORS
IRON ADDITIONS
IRON ALLOYS
MINERALS
MOESSBAUER EFFECT
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITE
PEROVSKITES
PHYSICAL PROPERTIES
QUANTITY RATIO
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
VALENCE
VARIATIONS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES