The compensation effect (Meyer–Neldel rule) on [AlO4/h+]0 and [TiO4/M+]0 paramagnetic centers in irradiated sedimentary quartz

• Published in: AIP advances 2020-07, Vol.10 (7), p.075114-075114-8
• Main Authors: Benzid, Khalif, Timar Gabor, Alida
• Format: Article
• Language: English
• Subjects: Activation energy; Cation exchanging; Defects; Electron paramagnetic resonance; Electron spin; Gamma rays; Heat exchange; Irradiation; Quartz; Spin resonance; Thermal stability
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/5.0005161

The effect of thermal excitation on paramagnetic defects in natural sedimentary quartz irradiated with different doses of gamma radiation was studied using electron spin resonance (ESR) spectroscopy. We report a variation in the activation energy and the frequency factor for [AlO4/h+]0 and [TiO4/M+]0 paramagnetic defects with the gamma dose, for a dose range investigated between ∼100 Gy and ∼40 000 Gy. Our results indicate that both [AlO4/h+]0 and [TiO4/M+]0 defects are less thermally stable above 1 kGy–2 kGy than below this dose range. The correlation between the two kinetic parameters (activation energy and frequency factor) satisfies the Meyer–Neldel rule. A linear correlation was found between the amplitude of the ESR signals of [AlO4/h+]0 and [TiO4/M+]0 paramagnetic defects corresponding to different doses after the application of thermal treatments in the pulse annealing procedure. We propose a mechanism involving the exchange of the cation, assigned mainly to Li+ here, between the two defects. Under irradiation, the cation is removed from [AlO4/M+]0 (forming [AlO4/h+]0) to [TiO4]− (forming [TiO4/M+]0), while under heating, the reverse mechanism takes place. The migration energy of the cation from one defect to another was found to be about 51 meV, corresponding to a temperature of about 325 °C.