Energetics of radiation damage in natural zircon (ZrSiO4) |
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| Authors: | Susan Ellsworth Alexandra Navrotsky Rodney C Ewing |
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| Institution: | 1. Department of Geological and Geophysical Sciences and Princeton Materials Institute, Princeton University, 08544, Princeton, New Jersey, USA
2. Department of Earth and Planetary Sciences, University of New Mexico, 87131, Albuquerque, New Mexico, USA
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| Abstract: | Transposed temperature drop calorimetry at 1000 °C was performed on natural zircons (ZrSiO4) from Sri Lanka that were partially to completely metamict due to α-decay event damage (0.06 to 11.7×1015 α-decay events/mg). The enthalpy of annealing at room temperature (ΔHanneal) varies sigmoidally as a function of radiation dose. ΔHanneal reaches a saturation plateau at radiation doses greater than 5×1015 α-decay events/mg. The annealing of several samples to a crystalline structure with broadened diffraction peaks does not significantly affect the enthalpy of annealing. The large magnitude of the enthalpy of annealing plateau, ?59±3 kJ/mol, suggests that the damage to the structure is pervasive on the scale of Angstroms, consistent with the loss of mid-range order characteristic of a glass. The energetics are consistent with, but do not require, chemical heterogeneity caused by micro-domains of amorphous SiO2-rich and ZrO2-rich regions in the metamict state. |
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