Static and Dynamic Disorder in Metastable Phases of Tin Oxide

The multistage transformation of Sn3O4 to SnO2 in an oxygen-free atmosphere has been studied using hydrothermally synthesized samples, both pristine and heated, with in situ X-ray diffractometry, Raman spectroscopy, differential scanning calorimetry, dielectric spectroscopy, and ex situ X-ray photoelectron and nuclear magnetic resonance spectroscopies. Experimental evidence consistently shows that, beginning from 250 °C, Sn3O4 converts to Sn2O3 and, from 350 °C, to SnO2, accompanied by the formation of metallic tin. These two stages are associated with frequency-dependent dielectric losses, as revealed by impedance measurements, which also indicate a significant conductivity of 1.78 eV in activation energy. It is speculated that the relaxation-like processes relate to the transition from static to dynamic disorder and then to order in the oxygen sublattice.