| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1681339 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms | 2013 | 4 Pages |
•Natural pumpellyite mineral presents superposition bands around 900 and 1060 nm due Fe2+and Fe3+.•High temperature annealing influences the EPR and OA spectra.•The behavior of EPR line for 800 and 900 °C can be attributed to forbidden dd transitions due the Fe3+.
Natural silicate mineral of pumpellyite, Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O), point group A2/m, has been studied concerning high temperature annealing and γ-radiation effects on Optical Absorption (OA) and Electron Paramagnetic Resonance (EPR) properties. Chemical analysis revealed that besides Si, Al, Ca and Mg, other oxides i.e., Fe, Mn, Na, K, Ti and P are present in the structure as impurities. OA measurements of natural and annealed pumpellyite revealed several bands in the visible region due to spin forbidden transitions of Fe2+ and Fe3+. The behaviour of bands around 900 and 1060 nm, with pre-annealing and γ radiation dose, indicating a transition Fe2+ → e− + Fe3+. On the other hand, EPR measurements reveal six lines of Mn2+, and satellites due to hyperfine interaction, superimposed on the signal of Fe3+ around of g = 2. For heat treatment from 800 °C the signal grows significantly and for 900 °C a strong signal of Fe3+ hides all Mn2+ lines. The strong growth of this signal indicates that the transitions are due to Fe3+ dipole–dipole interactions.
