Effects of Time and Temperature of Firing on Fe-rich Ceramics Studied by Mössbauer Spectroscopy and 2D 1H-NMR Relaxometry

The combined effect of firing temperature and soaking time on the microstructure of iron-rich porous ceramics has been studied by 57Fe-Mössbauer spectroscopy and 2D 1H nuclear magnetic resonance (NMR) relaxometry by using a single-sided probe. The application of the relaxation correlation method to water-saturated ceramics provides information about the firing-induced modifications in both porous and magnetic properties by the concurrent measurement of longitudinal (T1) and transverse (T2) relaxation times, respectively. The comparison between the characterization of firing-induced rearrangements in the iron-bearing species provided by Mössbauer and 1H-NMR analyses shows the high sensitivity of the T1-T2 NMR correlation technique to even subtle modifications in the magnetic behaviour of Fe-bearing species. Moreover, the single-sided NMR approach has allowed performing depth-resolved measurements at the millimeter-scale to non-invasively study the microstructural heterogeneities associated with non-uniform firing effects inside the ceramic material.