New k-phase materials, k-(ET) sub 2 Cu(N(CN) sub 2 )X: X = Cl, Br and I: The synthesis, structure and superconductivity above 11 K in the Cl ( Tc = 12. 8 K, 0. 3 kbar) and Br( Tc = 11. 6 K) salts

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

OSTI ID:6549234

Wang, H H; Carlson, K D; Geiser, U; Kini, A M; Schultz, A J; Williams, J M; Montgomery, L K; Kwok, W K; Welp, U; Vandervoort, K G; Boryschuk, S J; Strieby Crouch, A V; Kommers, J M; Watkins, D M ^[1]; Schirber, J E; Overmyer, D L ^[2]; Jung, D; Novoa, J J; Whangbo, M H ^[3]

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1. Argonne National Lab., IL (USA)
2. Sandia National Labs., Albuquerque, NM (USA)
3. North Carolina State Univ., Raleigh, NC (USA)

The syntheses, structures, selected physical properties, and band electronic structures of three copper (I) dicyanamide halide salts of bis(ethylenedithio)tetrathiafulvalene ({kappa}-(ET){sub 2}Cu(N(CN){sub 2})X, where X = Cl, Br, and I) are discussed. X-ray crystallographic studies demonstrate that the three derivatives are isostructural. The bromide salt is an ambient pressure superconductor with an inductive onset at 11.6 K and a resistive onset at 12.5 K. {kappa}-(ET){sub 2}Cu(N(CN){sub 2})Cl exhibits the highest reported superconducting transition temperature ({Tc} = 12.8 K, 0.3 kbar) for an organic superconductor, once a semiconductor-semiconductor transition (42 K) is suppressed. The application of GE varnish or Apiezon N grease to crystals of {kappa}-(ET){sub 2}Cu(N(CN){sub 2})Cl provides sufficient stress to induce superconductivity at ambient pressure.'' Crystals of the iodide remain metallic to {approximately}150 K, where they become weakly semiconductive. No sign of superconductivity was detected at pressures (hydrostatic and shearing) up to 5.2 kbar and at temperatures as low as 1.1 K. The band electronic structures of the three salts are essentially identical. The differences in superconducting properties are explained in terms of differences in lattice softness, which are strongly influenced by short C-H{hor ellipsis}donor and C-H{hor ellipsis}anion contacts. 17 refs., 2 figs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC04-76DP00789; FG05-86ER45259; W-31109-ENG-38
• OSTI ID: 6549234
• Report Number(s): SAND-90-2470C; CONF-9009257-1; ON: DE91000029
• Resource Relation: Conference: International conference on science and technology of synthetic metals, Tuebingen (Germany, F.R.), 2-7 Sep 1990
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER COMPOUNDS
SUPERCONDUCTIVITY
CYANAMIDES
SALTS
SUPERCONDUCTORS
SYNTHESIS
ELECTRONIC STRUCTURE
HALIDES
CARBONIC ACID DERIVATIVES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HALOGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSICAL PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360603* - Materials- Properties
360601 - Other Materials- Preparation & Manufacture
656100 - Condensed Matter Physics- Superconductivity