<sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes
This paper presents the results of <sup>57</sup>Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)<sub>4</sub>(Fe<sup>2+</sup>,Mg)<sub>2</sub>(Ti,Fe<sup>3+</sup>)<sub>3</sub>Si<...
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MDPI AG
2023-10-01
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| Online Access: | https://www.mdpi.com/2075-163X/13/11/1395 |
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| author | Dariusz Malczewski Agnieszka Grabias Maria Dziurowicz Tomasz Krzykawski |
| author_facet | Dariusz Malczewski Agnieszka Grabias Maria Dziurowicz Tomasz Krzykawski |
| author_sort | Dariusz Malczewski |
| collection | DOAJ |
| description | This paper presents the results of <sup>57</sup>Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)<sub>4</sub>(Fe<sup>2+</sup>,Mg)<sub>2</sub>(Ti,Fe<sup>3+</sup>)<sub>3</sub>Si<sub>4</sub>O<sub>22</sub> after annealing in argon from 673 to 1273 K for one hour. Radioactive elements in metamict minerals damage crystal structure on geologic time scales primarily due to recoil nuclei from α-decay of <sup>238</sup>U, <sup>232</sup>Th, <sup>235</sup>U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogs for the study of radiation effects in high-level nuclear waste. Analyses were performed on fragments of a perrierite sample collected from granitoids near Amherst, Virginia (USA). Electron microprobe and gamma-ray spectrometry recorded Fe concentrations of 4.7 wt.% and Th and U concentrations of 0.64 and 0.06 wt.%, respectively. The calculated total absorbed α-dose was 7.8 × 10<sup>15</sup> α-decay mg<sup>−1</sup>. The Mössbauer spectrum of the untreated sample can be fitted to two Fe<sup>2+</sup> and two Fe<sup>3+</sup> doublets in octahedral coordination with a relative ΣFe<sup>2+</sup>/ΣFe of 0.63. For samples annealed at 1173 K and 1273 K, spectra show a decrease in the total contribution of Fe<sup>2+</sup> to 0.58 due to dehydroxylation associated with the simultaneous oxidation of post-metamict Fe<sup>2+</sup> to Fe<sup>3+</sup>. In the examined perrierite, Fe<sup>2+</sup> occurs in structural positions B and C(1). The broad, predominant Fe<sup>3+</sup> doublet observed in the spectrum of the unannealed sample splits into two components at 973 K interpreted to represented positions C(1) and C(2) in the perrierite structure. The Mössbauer spectra show a prominent decrease in the width of the high-energy absorption peak representing Fe<sup>2+</sup> components with increasing temperature. The variation in the width of this peak versus the annealing temperature seems to be an indicator of thermally induced recrystallization. Based on the exponential dependence of the derivative function of the parameter with the inverse temperature and using an Arrhenius plot, an activation energy (E<sub>A</sub>) of 0.73 eV was determined for thermally-induced recrystallization. Corresponding XRD data show progressive recrystallization with increasing annealing temperature. The XRD pattern of the fragment annealed at 1273 K indicates that highly metamict perrierite recrystallized to the pre-metamict state that can be indexed to the C2/m space group. |
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| spelling | doaj.art-bd00d334e2374490ba20dc4a4bd646c52023-11-24T14:57:32ZengMDPI AGMinerals2075-163X2023-10-011311139510.3390/min13111395<sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization ProcessesDariusz Malczewski0Agnieszka Grabias1Maria Dziurowicz2Tomasz Krzykawski3Institute of Earth Sciences, University of Silesia, Będzińska 60, 41-200 Sosnowiec, PolandŁukasiewicz Research Network—Institute of Microelectronics and Photonics, Al. Lotników 32/46, 02-668 Warszawa, PolandInstitute of Earth Sciences, University of Silesia, Będzińska 60, 41-200 Sosnowiec, PolandInstitute of Earth Sciences, University of Silesia, Będzińska 60, 41-200 Sosnowiec, PolandThis paper presents the results of <sup>57</sup>Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)<sub>4</sub>(Fe<sup>2+</sup>,Mg)<sub>2</sub>(Ti,Fe<sup>3+</sup>)<sub>3</sub>Si<sub>4</sub>O<sub>22</sub> after annealing in argon from 673 to 1273 K for one hour. Radioactive elements in metamict minerals damage crystal structure on geologic time scales primarily due to recoil nuclei from α-decay of <sup>238</sup>U, <sup>232</sup>Th, <sup>235</sup>U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogs for the study of radiation effects in high-level nuclear waste. Analyses were performed on fragments of a perrierite sample collected from granitoids near Amherst, Virginia (USA). Electron microprobe and gamma-ray spectrometry recorded Fe concentrations of 4.7 wt.% and Th and U concentrations of 0.64 and 0.06 wt.%, respectively. The calculated total absorbed α-dose was 7.8 × 10<sup>15</sup> α-decay mg<sup>−1</sup>. The Mössbauer spectrum of the untreated sample can be fitted to two Fe<sup>2+</sup> and two Fe<sup>3+</sup> doublets in octahedral coordination with a relative ΣFe<sup>2+</sup>/ΣFe of 0.63. For samples annealed at 1173 K and 1273 K, spectra show a decrease in the total contribution of Fe<sup>2+</sup> to 0.58 due to dehydroxylation associated with the simultaneous oxidation of post-metamict Fe<sup>2+</sup> to Fe<sup>3+</sup>. In the examined perrierite, Fe<sup>2+</sup> occurs in structural positions B and C(1). The broad, predominant Fe<sup>3+</sup> doublet observed in the spectrum of the unannealed sample splits into two components at 973 K interpreted to represented positions C(1) and C(2) in the perrierite structure. The Mössbauer spectra show a prominent decrease in the width of the high-energy absorption peak representing Fe<sup>2+</sup> components with increasing temperature. The variation in the width of this peak versus the annealing temperature seems to be an indicator of thermally induced recrystallization. Based on the exponential dependence of the derivative function of the parameter with the inverse temperature and using an Arrhenius plot, an activation energy (E<sub>A</sub>) of 0.73 eV was determined for thermally-induced recrystallization. Corresponding XRD data show progressive recrystallization with increasing annealing temperature. The XRD pattern of the fragment annealed at 1273 K indicates that highly metamict perrierite recrystallized to the pre-metamict state that can be indexed to the C2/m space group.https://www.mdpi.com/2075-163X/13/11/1395metamict perrieriteMössbauer spectroscopyX-ray diffractionhigh-temperature annealingactivation energy |
| spellingShingle | Dariusz Malczewski Agnieszka Grabias Maria Dziurowicz Tomasz Krzykawski <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes Minerals metamict perrierite Mössbauer spectroscopy X-ray diffraction high-temperature annealing activation energy |
| title | <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes |
| title_full | <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes |
| title_fullStr | <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes |
| title_full_unstemmed | <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes |
| title_short | <sup>57</sup>Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes |
| title_sort | sup 57 sup fe mossbauer spectroscopy and x ray diffraction of annealed highly metamict perrierite activation energy and recrystallization processes |
| topic | metamict perrierite Mössbauer spectroscopy X-ray diffraction high-temperature annealing activation energy |
| url | https://www.mdpi.com/2075-163X/13/11/1395 |
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