An investigation on the activation energy and the enthalpy of the primary crystallization of glass–ceramic Bi-rich BSCCO HTc superconductors

The transformation of amorphous Bi-rich BSCCO (Bi3Sr2Ca2Cu3O12−x) to a superconductive crystalline material has been characterized by structural, thermal and transport measurements. The activation energy and enthalpy data of amorphous materials are examined in terms of analysis developed for non-isothermal crystallization studies. Two groups of samples were prepared. The first group was glass pieces (8×8×2 mm3) of material, and the second group was the same glass material grained and powdered (∼1–50 μm). Four different heating rates were used for differential scanning calorimetry and differential thermal analysis. The both thermal analysis indicated exothermic crystallization peaks at 467–489 °C for powdered and 472–490 °C for bulk samples depending on the heating rates. The enthalpy of the first crystallization of the samples varied between 40–107 and 30–35 J g−1 powdered and bulk materials, respectively. The crystallization activation energies of the samples were found to be 299 and 349 kJ mol−1 for powdered and bulk samples, respectively. The best electrical performance was obtained at 100 K for Tc and 90 K for Tzero. The highest thermal conductivity result was found to be 3.36 mW cm−1 K−1. The active phonon modes of the system was also found using the Fourier transform infrared analysis. The surface and the polished cross-sections of the samples and evolution of the phases formed were examined by scanning electron microscopy.