One of the basic characteristics of ceramic materials is their polycrystalline state. It means that, besides the possible presence of amorphous phases, they are mainly made of an assembly of crystals having different sizes, shapes and relative orientations. The intrinsic physical properties of a single crystal are determined by its chemical composition and structural interatomic arrangement, which can be managed as a function of external constraints like temperature, pressure or stresses, that promote solid-state phase transitions (SPT).  To fully understand the physical behavior of ceramic materials, it is necessary to understand the influence of their polycrystalline nature, and more generally of their microstructure, at all relevant scales, as well as the interdependence of their physical responses to external solicitation (see for example [1]). One of the convenient approaches of this general question is to follow the structural and microstructural evolutions in situ at the quantitative level during the relevant external stimulus.
SPTs are often associated with transformations that occur at the mesoscale and generate structural defects such as dislocations, twinning, stacking faults, strain fields, etc. Such defects can be studied quantitatively in the reciprocal space through high-resolution X-ray diffraction experiments. Over the past decade, the widespread use of 2D solid-state detectors at synchrotron radiation sources has promoted the development of 3D-reciprocal space mapping (RSM) on a timescale that enables to follow the sample evolutions as a function of external stimuli. We have recently shown that this method can be used even at very high temperatures on ceramic materials [1-3] allowing to follow in situ the appearance of crystallographic variants and twins through SPTs. The potential of this approach will be illustrated by the in situ study of two successive phase transitions in pure zirconia bulk ceramics. Moreover, since the SPT occurs under huge stresses [4], the reciprocal lattice nodes (RLNs) are embedded in a large, 3-dimensional, diffuse scattering signal that is clearly detectable. The crystallographic interpretation of RLN splitting and the diffuse scattering signal associated with the phase transitions can provide important insights into the behavior of ceramic materials under external stress and will be discussed during the talk according to [1, 3].
[1] R. Guinebretière, T. Ors, V. Michel, E. Thune, M. Huger, S. Arnaud, N. Blanc, N. Boudet, O. Castelnau, “Coupling between elastic strains and phase transition in dense pure zirconia polycrystals” Phys. Rev. Mater.  6 (2022) 013602.
[2] R. Guinebretière, S. Arnaud, N. Blanc, N. Boudet, E. Thune, D. Babonneau, O. Castelnau “Full reciprocal space mapping up to 2000 K under controlled atmosphere: the multi-purpose QMAX furnace” J. Appl. Cryst. 53 (2020) 650-661.
[3] R.R.P. Purushottam Raj Purohit, D.P. Fowan, E. Thune, S. Arnaud, G. Chahine, N. Blanc, O. Castelnau, R. Guinebretière “Phase transition and twinning in polycrystals probed by in situ high temperature 3D reciprocal space mapping” Appl. Phys. Lett. 121 (2022) 181901
[4] T. Ors, F. Gouraud, V. Michel, M. Huger, N. Gey, J.S. Micha, O. Castelnau, R. Guinebretière “Huge local elastic strains in bulk nanostructured pure zirconia materials” Mater. Sci. Eng.A 806 (2021) 140817.