New Reaction Routes for Preparing Single-Phase Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10 Powders from Stoichiometric Mixtures

Abstract
Single-phase Tl2CaBa2Cu2O8 and Tl2Ca2Ba2Cu3O10 powders were prepared from stoichiometric mixtures by the following two reactions: (1) CaBa2CuO4+Tl2O3+CuO→Tl2CaBa2Cu2O8 and (2) Tl2CaBa2Cu2O8+CaO+CuO→Tl2Ca2Ba2Cu3O10. Single-phase powders were obtained at 830°C for the first reaction, and at 870°C for the second reaction. At these temperatures, the extent of powder melting and the rate of Tl loss were small. Powders thus prepared showed superconducting temperatures (both the zero-resistivity and diamagnetic onset temperatures) of above 110 K and a saturation Meissner effect of 20% of (-1/4π) at a field of 20 G.