Growth of Tetragonal Zirconia Coatings by Reactive Sputter Deposition

Zirconia coatings were produced by reactive dc magnetron sputter deposition, using a system with multiple sputter sources and a biased substrate stage. Tetragonal zirconia with either a random orientation or a highly (111) preferred orientation was formed by applying a substrate bias. Coating grown with no substrate bias had the equilibrium monoclinic structure. X-ray diffraction and transmission electron microscopy analyses revealed that bias sputtering could effectively decrease crystalline size in the as-deposited coating, which resulted in room-temperature stabilization of the tetragonal phase. The fraction of tetragonal phase, the desired phase for transformation-toughening behavior, was strongly dependent on the substrate bias and post-deposition annealing temperature.