Thermal expansion and high temperature structure evolution of zoisite by single-crystal X-ray and neutron diffraction
Articolo
Data di Pubblicazione:
2012
Citazione:
Thermal expansion and high temperature structure evolution of zoisite by single-crystal X-ray and neutron diffraction / F. Cámara, G.D. Gatta, M. Meven, D. Pasqual. - In: PHYSICS AND CHEMISTRY OF MINERALS. - ISSN 0342-1791. - 39:1(2012 Jan), pp. 27-45.
Abstract:
The thermo-elastic behaviour and the temperature-induced structure evolution of a natural Fe-free zoisite have been investigated by in situ single-crystal X-ray and neutron diffraction. Neither discontinuities in volume expansion nor changes in symmetry have been observed up to 1,023 K. Zoisite shows a negative thermal expansion along [100] at T>700 K, while a continuous positive expansion occurs on the (100) plane. Two different regimes in the anisotropic thermal behaviour of zoisite can be distinguished (i.e. at T<700 K and T>700 K), corresponding to an increase in the volumetric thermal expansion at T>700 K. The structure evolution with temperature has been described by a series of X-ray and neutron refinements at different temperatures. In particular, the M(3) polyhedra show a significant octahedral flattening and expansion in the equatorial plane with T. All [SiO4] tetrahedra show a regularization with increasing T. The neutron refinements show no change in the configuration of the hydrogen bonding at least up to 873 K. The effects of the T-induced main deformation mechanisms on the anisotropic elastic behaviour of zoisite are discussed. A comparison with the thermal behaviour of epidote has been carried out.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Zoisite; Thermal expansion; Single-crystal X-ray diffraction; Single-crystal neutron diffraction; Hydrogen bonding
Elenco autori:
F. Cámara, G.D. Gatta, M. Meven, D. Pasqual
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