ENHANCEMENT OF ORTHORHOMBICITY AND SUPERCONDUCTIVITY IN ARGON PREHEATED EUSRBACU3O6+Z

We have studied the structural and superconducting properties of the s uperconductor EuSrBaCu3O6+z. This compound when annealed in oxygen at 450-degrees-C showed an orthorhombic structure in contradiction to the earlier published data. When the same sample was heated in argon foll owed by oxygen annealing, the orthorhombicity (b-a)/(b+a) increased fr om 2.86 X 10(-3) to 6.96 X 10(-3) and T(c) from 80 to 87 K. Further, t here was an enhancement in the shielding and the intergranular critica l current. A combination of several factors such as changes in the Cu1 -apical oxygen distance, chain oxygen ordering and hole density may qu alitatively account for the observed data.