Processing and crystallographic structure of non-equilibrium Si-doped HfO₂

Si-doped HfO₂ was confirmed to exist as a non-equilibrium state. The crystallographic structures of Si-doped HfO₂ were studied using high-resolution synchrotron X-ray diffraction and the Rietveld refinement method. Incorporation of Si into HfO₂ and diffusion of Si out of (Hf,Si)O2 were determined as a function of calcination temperature. Higher thermal energy input at elevated calcination temperatures resulted in the formation of HfSiO4, which is the expected major secondary phase in Si-doped HfO₂. The effect of SiO2 particle size (nano- and micron-sized) on the formation of Sidoped HfO₂ was also determined. Nano-crystalline SiO2 was found to incorporate into HfO₂ more readily.