Natural silicate mineral of pumpellyite, Ca2MgAl 2(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 Mn 2+, 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.
|Número de páginas||4|
|Publicación||Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms|
|Estado||Publicada - 2013|
|Publicado de forma externa||Sí|
Nota bibliográficaFunding Information:
We would like to thank Ms. E. Somesari and Mr. C.Gaia for kindly carrying out irradiation of the samples. This work was supported by CAPES and FAPESP.