Anisotropic line broadening analysis in α- and β-cristobalite

β-cristobalite is the high-temperature crystalline phase of SiO2 at ambient pressure. It is metastable below 1740 K and undergoes a displacive transition to α-cristobalite around 540K. New data show that α-cristobalite displays an anisotropic powder diffraction line broadening, which we attribute to the domain formation that occurs upon symmetry loss at the phase transition. Our preliminary experiment on BM01 indicates that diffraction lines become sharper above the α-β transition. Here, we propose a high-resolution powder diffraction study of the α-β transition as a function of temperature on ID22 to obtain data precise enough for quantitative analysis of stress and size effects in the domain structure of α-cristobalite.