Annealing induced oxidation and transformation of Zr thin film prepared by ion beam sputtering deposition

Nanocrystalline α-Zr condensates deposited by ion beam sputtering on the NaCl (1 0 0) surfaces and then annealed at 100-750 °C in air. The phases present were identified by transmission electron microscopy to be nanometer-size α-Zr + ZrO, α-Zr + ZrO + c-ZrO2, c-ZrO2, c- + t-ZrO2, t-ZrO2, and t- + m-ZrO2 phase assemblages with increasing annealing temperature. The ZrO2 showed strong {1 0 0} preferred orientation due to parallel epitaxy with NaCl (1 0 0) when annealed between 150 and 500 °C in air. The c- and t-ZrO2 condensates also showed (1 1 1)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains.