Oriented superconducting YBa2Cu3O7thin films were deposited on yttria‐stabilized zirconia substrates by ion beam sputtering of a nonstoichiometric oxide target. The films exhibited zero‐resistance critical temperatures as high as 80.5 K without post‐deposition anneals. Both the deposition rate and theclattice parameter data displayed two distinct regimes of dependence on the beam power of the ion source. Low‐power sputtering yielded films with largecdimensions and lowTc’s. Higher power sputtering produced a continuous decrease in theclattice parameter and an increase in critical temperatures.