Structural evolution in reactive RF magnetron sputtered (Cr,Zr)2O3 coatings during annealing

Abstract Reactive RF-magnetron sputtering is used to grow Cr 0.28 Zr 0.10 O 0.61 coatings at 500 °C. Coatings are annealed at 750 °C, 810 °C, and 870 °C. The microstructure evolution of the pseudobinary oxide compound is characterized through high resolution state of the art HRSTEM and HREDX-maps, revealing the segregation of Cr and Zr on the nm scale. The as-deposited coating comprises α-(Cr,Zr) 2 O 3 solid solution with a Zr-rich (Zr,Cr)O x amorphous phase. After annealing to 750 °C tetragonal ZrO 2 nucleates and grows from the amorphous phase. The ZrO 2 phase is stabilized in its tetragonal structure at these fairly low annealing temperatures, possibly due to the small grain size (below ∼30 nm). Correlated with the nucleation and growth of the tetragonal-ZrO 2 phase is an increase in hardness, with a maximum hardness after annealing to 750 °C, followed by a decrease in hardness upon coarsening, bcc metallic Cr phase formation and loss of oxygen during annealing to 870 °C. The observed phase segregation opens up future design routes for pseudobinary oxides with tunable microstructural and mechanical properties.