Probing firing-induced changes in non-carbonate clay through 55Mn EPR techniques

Non-carbonate clay samples, fired in steps of 50 °C between 600 °C and 1000 °C, were examined through electron paramagnetic resonance (EPR) techniques (X- and Q-Band pulsed- and cw-EPR). X-band pulsed EPR and Q-Band pulsed- and cw-EPR techniques were able to spot 55Mn(II) signals out of the large iron background in the full range of firing temperatures, allowing one to follow the phase transformations through the evolution of the manganese signal. Q-Band pulsed EPR turned out to be particularly suitable to detect even small amounts of this ion in calcite, while the 55Mn hyperfine coupling constant, determined through Q-Band cw-EPR, could be used to detect transitions to the glassy phase.