RESISTANCE VERSUS TEMPERATURE MODEL FOR POROUS MULTIPHASED SUPERCONDUCTING MATERIALS AND ASSOCIATED PARAMETRIZATION METHOD FOR THE EXPERIMENTAL-DATA

We develop a resistance versus temperature model for porous multiphase d superconducting materials on the basis of percolation calculations. In parallel, we associate to the model a parametrization method for th e experimental data. Fitting of the continuum of R(T), or dR/dT points with the computed model is achieved with a limited number of paramete rs. These parameters only depend on physical properties of the investi gated materials (phases, superconductive state, porosity...). The agre ement between calculation results and experimental R(T) data for YBa2C U3O7-x and Bi2Sr2Ca2Cu3O10 films or wires demonstrates the fruitfulnes s of both the parametrization method and the ''porous model''. Thus it has been possible to estimate the critical temperatures (and widths o f their distributions) and the concentrations of the different phases present in some superconducting materials.