Ag2O as nucleating agent in the crystallization of superconducting phase in Bi2Sr2Ca4Cu5γ glass composition

Abstract The nucleating action of silver oxide (1 mol% Ag 2 O) in the crystallization of superconducting phase in Bi 2 Sr 2 Ca 4 Cu 5 O γ system is quite remarkable. The characteristics of these glass ceramics are found to depend chiefly upon the formation conditions of the initial glass composition and a subsequent phase separation. We observe from the SEM studies the evidence of highly textured growth. The presence of long platelet and square-like platelet-type particles could be explained on the basis of an orientation effect. Besides being influencing the structural properties markedly, the nucleating agent also affects the physical properties, in particular, the normal state resistivity (ϱ). The above effects result in broadening of X-ray diffraction lines and a change in slope, in the normal state region (190–220 K) of ϱ ( T ) plots. Out of the three procedures used to fit the ϱ ( T ) data, the usual linear fit ( ϱχT ) does not work out at all over the temperature range 140–300 K. On the other hand non-linear fits, ϱχT n ( n =0.5) and the piece-wise linear fits (140–200 K and 220–300 K) work out much better. These results are interpreted on the basis of a possible intergrowth of two superconducting phases.