The structure of the Zr atomic environment in a CaO - ZrO2 - SiO2 glass ceramic as a function of thermal treatments has been studied, combining X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and anomalous XRD (a-XRD) techniques. The analysis of XRD patterns demonstrates that the devitrification process proceeds through the partial segregation of Zr-depleted phases (wollastonite-like) and Zr-rich phases ( Zr oxides). The XAS and a-XRD measurements at the Zr K-edge have been exploited in order to obtain a closer insight into the atomic structure around the Zr atoms. In the as-quenched glass the Zr atom is sixfold coordinated to O atoms in an amorphous environment rich in Ca and Si. Thermal treatment firstly ( T = 1273 - 1323 K) causes partial segregation of Zr in the form of an oxide with a tetragonal zirconia (t-ZrO2) crystalline structure. Raising the temperature ( T = 1373 K) causes the formation of ZrO2 crystallites in the monoclinic crystallographic phase (baddeleyite, m-ZrO2). Analysis of the XAS data shows that a considerable amount of Zr remains in an amorphous calcium silicate phase.
Meneghini, C., Mobilio, S., Lusvarghi, L., Bondioli, F., Ferrari, A.M., Manfredini, T., et al. (2004). The structure of ZrO2 phases and devitrification processes in a Ca-Zr-Si-O-based glass ceramic: A combined a-XRD and XAS study. JOURNAL OF APPLIED CRYSTALLOGRAPHY, 37, 890-900 [10.1107/S0021889804022307].
The structure of ZrO2 phases and devitrification processes in a Ca-Zr-Si-O-based glass ceramic: A combined a-XRD and XAS study
MOBILIO, Settimio;
2004-01-01
Abstract
The structure of the Zr atomic environment in a CaO - ZrO2 - SiO2 glass ceramic as a function of thermal treatments has been studied, combining X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and anomalous XRD (a-XRD) techniques. The analysis of XRD patterns demonstrates that the devitrification process proceeds through the partial segregation of Zr-depleted phases (wollastonite-like) and Zr-rich phases ( Zr oxides). The XAS and a-XRD measurements at the Zr K-edge have been exploited in order to obtain a closer insight into the atomic structure around the Zr atoms. In the as-quenched glass the Zr atom is sixfold coordinated to O atoms in an amorphous environment rich in Ca and Si. Thermal treatment firstly ( T = 1273 - 1323 K) causes partial segregation of Zr in the form of an oxide with a tetragonal zirconia (t-ZrO2) crystalline structure. Raising the temperature ( T = 1373 K) causes the formation of ZrO2 crystallites in the monoclinic crystallographic phase (baddeleyite, m-ZrO2). Analysis of the XAS data shows that a considerable amount of Zr remains in an amorphous calcium silicate phase.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
