PHASE DIAGRAM OF BaO-Y 2 O 3 (La 2 O 3 )-CuO TERNARY SYSTEM

The phase diagrams of La2O3-CuO, BaO-CuO,Y2O3(La2O3)-CuO binary systems and BaO-La2O3CuO, BaO-Y2O3-CuO, ternary systems have been determined by means of X-ray diffraction, thermal analysis and measurement of superconductivity. In the CuO-rich region of two ternary systems, there are compounds: BaxLa2-xCuO4(x≤0.07), Ba2LaCu3O7+x, BaLaCu2O5+8, BaLa4Cu5 O14+8, BaLa2Cu2O6, Ba2YCu3O9-y, and BaY2CuO5. BaxLa2-xCuO4(x=0.07), BaLa4Cu5O14+8, Ba-LaCu2O5+8, and BaLa2Cu2O6 belong to tetragonal system with the lattice parameters a=5.356 , c=13.20; a=8.660, c=3.863; a=3.917, c=11.7; a=3.992, c=19.96 respectively. Ba2LaCu3O7+x belongs to orthorhomic structure with a=3.917, b=3.928, c=11.794 and space group Pmmm. Ba2YCu3O9-y is of a distorted orthorhombic perovskite structure with a=3.892, b=3.824, c=11.64 and space group Pmmm. BaY2CuO5 belongs to orthorhombic structure with a=7.123, b=12.126, c=5.649 and the space group Pbnm. The relationship between composition and superconductivity has been studied. The effect of sintering temperature on the structure and superconductivity of Ba2YCu3O9-y and a possible reason for superconductivity have been discussed.