Superconducting Bi2Sr2Ca1Cu2O8+y Glass-Ceramics with Different Melting Histories

Superconducting Bi2Sr2Ca1Cu2O8+y glass-ceramics were prepared by controlled crystallization of the corresponding composition glasses. We examined the effect of melting temperature (T m) of the glasses on the crystallization behavior and the T c of the resulting glass-ceramics. The crystallization behavior was considerably influenced by the Cu(II)/ΣCu ratio of the precursor glass, which varies to a considerable extent with T m. The lower Cu(II)/ΣCu ratio of the glass leads to formation of larger crystallites and higher excess oxygen absorption upon crystallization. The T c of the glass-ceramics obtained by the same heat treatment tends to increase with increasing T m of the mother glasses. This tendency of T c to increase may be explained in terms of oxygen content in the glass-ceramics.