High Pressure Synthesis of Oxides in Y-Ba-Cu-O System and its Fluorine Addition

Abstract

YBa₂Cu₃O ?? with y>7 and y<6.5 were prepared under high pressure conditions of 3GPa, 830°C, 8hrs. BaO₂ and BaCuO₂ were respectively used as barium source. Both phases of YBa₂Cu₃O ?? were tetragonal with a = 1/3c = 3.87A, c = 11.60Å and a = 3.86Å, c = 11.70Å respectively. They were semiconductors. YBa₂Cu₄O₈ was obtained with BaY₂F₈ from a mixture of Y₂O₃ : YF₃ : BaO₂ : CuO = 0.9 : 0.2 : 4 : 6 under conditions of 3GPa, 830°C, 8hrs. The product showed Tc around 90 K.