Abstract :
The effect of Pr on the superconductivity of PrBa2Cu3O7 implies that the cuprate-planes are not primary superconductors, because Pr-on-a-Ba-site (on one side of a cuprate plane) breaks Cooper pairs and destroys the superconductivity, while Pr-on-a-Pr-site (on the other side) does not adversely affect the superconductivity.
