HIGH-T//c SUPERCONDUCTIVITY IN Ln//2// minus //xBa//xCu//2O//5 (1. 0 less than equivalent to x less than equivalent to 1. 6) AND LnBa//2Cu//3O//7 (Ln equals Dy, Er, Tm, Yb AND Y) COMPOUNDS.

Structure and T//c data on LnBa//2Cu//3O//7 (Ln equals Dy, Ho, Er, Tm, Yb and Y) compounds are reported and discussed. No reentrant behavior has been noted in these high-T//c superconductors for Ln equals Er and Yb until 4. 2 K. Four-probe resistivity was measured in the range 77-300 K employing ultrasonically soldered In-contacts. An inductance bridge with carrier-frequency amplifier was used to quickly check the samples for superconductivity at and above 77 K. A calibrated test set-up was employed to measure the superconductivity transition by the magnetic susceptibility technique.