The 5d pyrochlore iridate family (R2Ir2O7, where R is a rare earth ion) has garnered significant attention due to its topological properties, such as Weyl semimetallic phases and axion insulator. However, the investigation of these properties been impeded by severe iridium loss during growth, which results in formation defects impurities. Herein, we demonstrate method for controlling impurities...