Synthesis of Superconductive Oxides by Vacuum Calcination Method

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Abstract
The vacuum calcination method (VCM) was developed to synthesize Ln-Ba-Cu-O group superconductive oxides represented by YBa2Cu3O7-x through solid phase reaction. When Y2O3, BaCO3 and CuO are used as raw materials in the form of powder in this method, the carbon content of the resultant calcinated product will be 1/10 that of the normal methods or lower. VCM powder is a mixture of Y2BaCuO5 and BaCu x O y , an unknown phase, and has extremely high activity because of oxygen content that is lower than the stoichiometric composition of YBa2Cu3O7-x . For this reason, it absorbs oxygen during sintering under an oxidizing atmosphere causing transition to the perovskite phase of YBa2Cu3O7-x , thus indicating excellent sinterability and high J c and magnetization.