High-temperature diffraction experiments and phase diagram of ZrO2 and ZrSiO4

Abstract High-temperature X-ray diffraction (XRD) experiments up to T = 2710 °C have been performed on ZrSiO 4 and ZrO 2 powders, using the container-less levitation technique. A two-dimensional imaging plate (IP) detector was used for short-time observation. The diffraction data in a wide area was projected in one dimension. The unit cell parameters, thermal expansions, and c/a ratios for ZrSiO 4 (space group I 4 1 / amd and Z = 4), tetragonal ZrO 2 (space group P 4 2 / nmc and Z = 2) and cubic ZrO 2 (space group F m 3 ‾ m $Fm3‾{}m$ and Z = 4) were measured to understand the high-temperature behaviors. The transition temperature between tetragonal and cubic ZrO 2 was specified to be between 2430 and 2540 °C. The pre-transitional behavior was observed around 2200 °C. As no clear change in unit cell volume is evident, the phase boundary between the tetragonal and the cubic phase has been shown to be a positive slope. The ZrO 2 and ZrO 2 –SiO 2 phase diagrams are proposed based on the chemical composition and the crystal structure.