ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
We exploited the large difference in the solubility of SiO2 and ZrO2 in H2O to constrain precisely the Gibbs energy of formation of zircon (ZrSiO4). Solubility in H2O was determined at 800°C, 1.2 GPa, by weight loss of synthetic zircon crystals. The experiments yielded fine-grained monoclinic ZrO2 as an incongruent solution product uniformly coating zircon crystals. Experiments on the ZrO2-coated zircon crystals were also carried out with an initially slightly SiO2-oversaturated fluid, causing weight gain by zircon regrowth. The mean SiO2 concentration for forward and reverse experiments was 0.069±0.010 mol/kg H2O (2σ). When combined with precise activity–composition measurements for aqueous SiO2, the data constrain the Gibbs free energy of zircon from its oxides at 298 K, 105 Pa, to be −19.30±1.16 kJ/mol (2σ). This determination is comparable in precision to the best measurements obtainable by more conventional methods, which suggests that determination of the thermochemical properties of other important ceramic materials may also be amenable to this method.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1551-2916.2005.00348.x
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