Synthesis of HTSC Re(Y)Ba2Cu3Ox powders:: the role of ionic radius

A comparison study of the calcination conditions for the synthesis of pure ReBa2Cu3Ox phases (Re: Y, Nd, Eu, Gd, Dy, Ho, Er) by solid state reaction from Re2O3, BaCO3 and CuO was carried out, X-ray diffraction analysis coupled with differential thermal analysis and hot-stage X-ray diffraction data were employed for this investigation, Thermal events occurring during reaction sequence and intermediate products are thoroughly discussed. It was found that the reaction rate for the ReBCO 123 phase formation depends on Re-ion size, decreasing as this size decreases and that the small Re-ion size powders present an increased instability. Due to their lower decomposition temperature and to their slower reaction rate, calcination of ReBCO systems of small Re ionic radius must be carried out at lower temperatures and at prolonged times, Calcination temperature can be increased when Re-ion size increases, (C) 1997 Elsevier Science B.V.