SUPERCONDUCTIVITY IN PRBA2CU3O7

Inhomogeneous granular superconductivity has been observed in PrBa2Cu3O7 films probed by microwaves, and in powders studied by electron spin resonance - although both the films and the powders have insulating do resistivities. The transition temperatures are approximate to 90 K with 90%-10% transition widths of approximate to 20 K or less. We interpret this as meaning (i) that small regions of PrBa2Cu3O7 superconduct, (ii) that perfect PrBa2Cu3O7 superconducts in the vicinity of the Cu-O chains, (iii) that cuprate-plane models of superconductivity are invalid, and (iv) that Ba-site Pr ions break pairs and destroy superconductivity.