Thermal expansion anisotropy in ceramics probed by in situ synchrotron X-ray diffraction at the poly- and single crystal scales
FOWAN D. 1, MOUIYA M. 1,2, PURUSHOTTAM RAJ PUROHI R. 3, MICHA J. 3, CHAHINE G. 4, BLANC N. 5, CASTELNAU O. 6, THUNE E. 1, GUINEBRETIERE R. 4
1 Institut de Recherche sur les Matériaux Céramiques (IRCER)/Université de Limoges, Limoges, France; 2 SMN/Université polytechnique Mohammed VI (UPM6), Ben Guerir, Morocco; 3 CEA-IRIG-MEM-CNRS/Université de Grenoble Alpes, Grenoble, France; 4 CEA-IRIG-MEM-CNRS/Université de Grenoble Alpes, Grenoble, France; 5 CNRS-Institut Néel/Université de Grenoble Alpes, Grenoble, France; 6 PIMM, ENSAM, CNAM, HESAM, Paris, France
The b-Al2TiO5 phase crystalizes in an orthorhombic structure according to the Cmcm space group, which is characterized by a strong anisotropic thermal expansion, negative along the -axis. The aluminum titanate polycrystalline materials therefore have a low macroscopic thermal expansion [1]. After sintering, they generally include a significant amount of microcracks leading to high overall flexibility [1]. In addition, during cooling down, below 1300 °C, b-Al2TiO5 is transformed into a-Al2O3 and TiO2. This decomposition can be avoided by the formation of solid solutions with appropriate cations [2].
We developed two X-ray diffraction experimental approaches to determine thermal expansion anisotropy on aluminum titanate bulk materials doped with iron and sintered according to different heat treatments [1]. All the measurements have been performed in situ as a function of the temperature using two different synchrotron beamlines at the ESRF in Grenoble. The first approach allows us, using a monochromatic X-ray beam, to measure the variation of lattice parameters averaged over all the diffracting crystals. The second approach consists to use a submicronic polychromatic beam for probing the lattice parameter variations inside one of the crystals as function of temperature up to 1250 °C. This was possible thanks to the Qmax-V2 furnace [3] and a new method of data processing based on the neural network [4].
[1] C. Babelot, A. Guignard, M. Huger, C. Gault, T. Chotard, T. Ota, N. Adachi, J. Mater. Sci., 46 (2011) 1211-1219.
[2] T. Korim, Ceram. Intern., 35 (2009) 1671?1675.
[3] R. R. P. Purushottam Raj Purohit, D. Fowan, S. Arnaud, N. Blanc, J.S. Micha, R. Guinebretière, O. Castelnau, submitted to J. Appl. Cryst.
[4] R. R. P. Purushottam Raj Purohit, S. Tardif, O. Castelnau, J. Eymery, R. Guinebretiere, O. Robach, T. Ors, J.S. Micha, J. Appl. Cryst. 55 (2022) 737-750.