| Abstract
| - Rietveld analyses performed on high-temperature X-ray (HTXRD) and neutron (HTND)powder patterns of β-(Zr2O)(PO4)2 have allowed us to follow accurately the thermal variationsof the cell parameters and to explain its strong dilatometric anisotropy in terms of structuraldistortions. It appeared that the anomaly resulted from two simultaneous mechanicaleffects: libration movements of the bridging oxygen atoms related to a rocking of the ZrO7and PO4 polyhedra and a rotation effect resulting from electrostatic repulsions between ZrIVcations of neighbor polyhedra. Both effects lead to a strong shrinkage of the b parameterand contribute to the ultralow overall expansion that has made β-(Zr2O)(PO4)2 famous as athermal-shock resistant material.
- The thermal-shock resistance of β-(Zr2O)(PO4)2, due to its ultralow expansion, results from two simultaneous mechanisms observed by neutron diffraction: the libration of bridging oxygen atoms, related to the classical polyhedra rocking, and an original structural folding arising from cations repulsions.
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