Synthesis and properties of polycrystalline Tl sub 2 Ba sub 2 CaCu sub 2 O sub x and Tl sub 2 Ba sub 2 Ca sub 2 Cu sub 3 O sub x

Conference · Mon Jan 01 04:00:00 EST 1990

OSTI ID:7108897

Vogt, G J; Phillips, D S

Polycrystalline samples of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub x} and Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} superconductors with high (>95 wt %) phase purity were prepared by a solid state reaction of Tl{sub 2}O{sub 3} with a mixture of BaCuO{sub 2}, Ca{sub 2}CuO{sub 3}, and CuO. Starting compositions of Tl{sub 1+{delta}}BaCaCu{sub 2}O{sub x} and Tl{sub 2+{delta}}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} were fired in semi-sealed reaction vessels for durations of 12 to 48 hours in flowing oxygen with low, reproducible thallium losses. Samples fired at temperatures below 870{degrees}C produced predominately the 2212 phase, while samples above 870{degrees}C yielded the 2223 phase. While pressed mixed oxides reacted in a single firing step produced low-density ({le}50% theoretical) material, samples prepared by a two-step sequence of reactive calcination, intermediate grinding, and sintering yielded higher density material (>70% theoretical). The sintered polycrystalline superconductors were characterized by x-ray diffraction, reflected light and electron microscopy, magnetic susceptibility, and dc transport resistivity. Critical current density measurements by direct transport and magnetic moment hysteresis methods are presented for the denser samples. Transport J{sub c} values up to 300 A/cm{sup 2} at 75 K were observed for moderately dense material (5.2 g/cm{sup 3}, 74% theoretical) in transverse H fields up to 10 kOe. 10 refs., 16 figs.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/CE
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 7108897
• Report Number(s): LA-UR-90-449; CONF-900287--1; ON: DE90007528
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
CURRENT DENSITY
DENSITY
DIFFRACTION
FABRICATION
GRAIN BOUNDARIES
HYSTERESIS
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PELLETS
PHYSICAL PROPERTIES
SCATTERING
SINTERING
SUPERCONDUCTORS
SYNTHESIS
THALLIUM COMPOUNDS
THALLIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION