Radiation-induced defects in quartz. IV. Thermal properties and implications

• Published in: Physics and chemistry of minerals Vol. 36; no. 8; pp. 421 - 430
• Main Authors: Pan, Yuanming, Hu, Baoqun
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2009; Springer Nature B.V
• Subjects: Bleaching; Cathodoluminescence; Crystal defects; Crystallography and Scattering Methods; Crystals; Decay; Defects; Diamagnetism; Earth and Environmental Science; Earth Sciences; Electron paramagnetic resonance; Gamma rays; Geochemistry; Isothermal annealing; Mineral Resources; Mineralogy; Original Paper; Peroxy radicals; Quartz; Radiation effects; Single crystals; Spectrum analysis; Thermal properties; Thermodynamic properties; Thermoluminescence; Uranium; Peroxy radicals; Decay kinetics; Single-crystal EPR; EPR dating; Cathodoluminescene; Natural quartz; Thermal stability; Thermoluminescence
• ISSN: 0342-1791; 1432-2021
• DOI: 10.1007/s00269-009-0288-0

The thermal stabilities and decay kinetics of three peroxy radicals (Centers #1, B and B′) and three other radiation-induced defects (#3, C′ and E 1 ′) in natural quartz from the high-grade McArthur River uranium deposit (Athabasca basin, Canada) have been investigated by isochronal and isothermal annealing experiments and electron paramagnetic resonance (EPR) spectroscopy. Single-crystal EPR spectra of isochronally (2 h) annealed quartz show that these centers all grow in intensity to 280°C and then decay with further increase in temperature, but their disappearance temperatures differ markedly and depend on the initial concentrations (e.g., Center #1 in a dark smoky quartz is annealed out at 380°C, B and B′ at 420°C and #3 and C′ at 580°C). The isothermal decay processes of these centers are all of the second order type. The calculated activation energies for the peroxy radicals [#1 and B + B′ at 0.36 (9) and 0.83 (8) eV, respectively] are smaller than those of Centers #3, C′ and E 1 ′ [1.09 (8), 1.24 (8) and 1.45 (7) eV, respectively]. Gamma-ray irradiations of thermally bleached quartz restore a fraction of the peroxy radicals, suggesting that their diamagnetic precursors are stable up to at least 800°C. The unusual decay characteristics of “peroxy radicals” in quartz reported in the literature are shown to most likely arise from multiple radiation-induced defects. These results have implications for not only applications of peroxy radicals in quartz for EPR dating but also better understanding of thermoluminescence and cathodoluminescence spectra of this mineral.