Effects of high-temperature annealing on ESR properties of solid solutions of garnet minerals

• TL peaks seen at 190, 270 and 340 °C in the garnet crystal.
• O2− ion, F+ center and Fe3+ ions observed in the ESR spectrum.
• Increase of cluster of Fe3+ ions are observed at high temperature annealing.

A garnet (G7) silicate mineral belonging to pyralspite subgroup was studied using the technique of electron spin resonance (ESR). This study shows that iron is present in G7 as isolated species as well as species coupled by dipolar interactions. The ESR data shows a gradual increase of cluster of Fe3+ ions accompanied by decrease of dipolar interactions and increase of possible exchange interactions at high temperature. The Fe2+→Fe3+ oxidation process occurs in the garnets as a function of annealing temperature. Thermoluminescence (TL) peaks at approximately 190 and 340 °C are observed in the irradiated G7 garnet. Investigations using the technique of ESR were carried out to identify the centers involved in the TL process.

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