The crystal growth kinetics of Bi2Sr2CaCu3Ox glass-ceramics

A glass of nominal Bi2Sr2CaCu3Ox composition prepared by rapid-quenching of the melt, showed a glass transition temperature of 438 °C, crystallization temperature of 454 °C and melting temperature of 860 °C at 10 °C/min heating rate. The activation energy for crystallization of the glass has been estimated to be 348 kJ/mol from non-isothermal differential scanning calorimetry (DSC). A Johnson–Mehl–Avrami analysis of DSC output gave an Avrami exponent n≈2.5 indicating growth on pre-existing nuclei, as shown by microscopy observations. A melt-quenched samples annealed at 830 °C for 72 h was superconducting with the transition temperatures at zero resistance (Tc, zero) and the onset (Tc, onset) of 68 and 98 K, respectively, and transition width ΔTc of 30 K.