Effect of annealing on grain growth and Y segregation behavior in tetragonal ZrO 2 thin film

Abstract In order to fabricate tetragonal yttria stabilized zirconia samples with large grain size, 3 mol% Y 2 O 3 doped zirconia thin films were grown on (0001) α‐Al 2 O 3 substrate by pulsed laser deposition (PLD) followed by subsequent high temperature annealing. The thin film samples were annealed at 1200°C, 1250°C, 1300°C, and 1350°C in order to obtain larger grain size without Y segregation. The microstructure and chemical composition of these annealed films were analyzed using atomic force microscopy, scanning transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. The as‐grown thin film was found to be composed of [111]‐oriented grains of ∼100 nm connected with small‐angle tilt boundaries. Based on analysis of annealed thin films, it was revealed that grain growth of tetragonal zirconia occurred anisotropically. Cross section scanning transmission electron microscopy observations revealed that such grain growth behavior is affected by the step‐terrace structures of the sapphire substrate. Energy‐dispersive X‐ray spectroscopy showed that Y was found to distribute almost uniformly below 1300°C but to segregate at the grain boundaries at 1350°C. As a conclusion, the 1300°C‐annealed sample shows the largest grain size with homogeneous Y distributions.