Papers Published

  1. Hammarstrom, H.M. and Bischoff, J.E. and Cocks, F.H., Chemical pressure analysis (CPA): yttrium, bismuth, thallium, and mercury based high-temperature superconductors, Mater. Chem. Phys. (Switzerland), vol. 40 no. 1 (1995), pp. 37 - 43 [0254-0584(94)01456-Q] .
    (last updated on 2007/04/10)

    Abstract:
    Chemical pressure analysis (CPA) is used to determine the anisotropic dependence of the critical temperature on the lattice parameters of Bi2Sr2CaCu2O8+x. CPA yields a quantitative expression relating Tc and lattice parameter values and offers a phenomenological approach to studying the effect of structure on superconductivity. Similar to previously reported results for YBa2Cu3O7-x and YBa2(Cu1-xFex)3O7-y, CPA for Bi2Sr2CaCu2O8+x reveals that the dependence of the critical temperature is strongly anisotropic and is influenced much more by chemical pressure than by physical (mechanical) pressure, per unit change in lattice parameter. A positive correlation is found between unit cell volume and Tc for Bi2Sr2CaCu2O8+x, but these parameters are negatively correlated for YBa2Cu3O7-x and YBa2(Cu1-xFex)3O7-y. Physical pressure results for both Tl2Ba2CaCu2Ox and HgBa2Cam-1CumO2m+2+δ indicate that increases of up to 28 K (10 GPa) and 30 K (45 GPa), respectively, can be obtained from these compounds, but sufficient lattice constant and elastic constant data for CPA are not yet available

    Keywords:
    bonds (chemical);high-temperature superconductors;lattice constants;superconducting transition temperature;thermodynamic properties;