HIGH-Tc OXIDE Y-Ba-Cu-O - NORMAL AND SUPERCONDUCTING PROPERTIES AND PHASES.

We have studied the effects of magnetic and non-magnetic alloying elements on the superconductivity of the high-T//c compound YBa//2Cu//3O//y by replacing Cu with Fe and Al. Both alloying elements Fe and Al change the crystal symmetry from orthorhombic to tetragonal and the normal conductivity from metal-like to insulator-like with increasing alloy concentration. The suppression rate of T//c due to Fe is found to be comparable to that due to Al, i. e. approximately equals 6 K/at%. The temperature gradient of the upper critical field, i. e. minus (dH//c//2/dT) of alloyed samples YBa//2(Cu//0//. //9//8Fe//0//. //0//2)//3O//y and YBa//2(Cu//0//. //9//9Al//0//. //0//1)//3O//y are about one half of approximately equals 3 T/K of YBa//2Cu//3O//y.