Electrical study of an unusual phase transformation in a Bi2Sr2Ca2Cu3O10+x whisker at room temperature

We report the observation of a phase transformation which can occur in a microscopic double phase BSCCO whisker at room temperature. We performed electrical resistivity measurements by thermally cycling the whisker in the range 78–300 K in a helium atmosphere and observed a decrease of the Bi-2223 phase amount in favour of the Bi-2212 phase, accompanied by an increase in the Tc of the Bi-2212 phase. A longer ageing of the whisker increased its resistance by about a factor of four at room temperature and caused a semiconducting behaviour at low temperature. We demonstrate that a simple electrical model can account for the experimental data and disentangle the contributions of the two phases.