Thermal behaviour of romarchite phase SnO in different atmospheres: a hypothesis about the phase transformation

A study was conducted on the transformation of SnO to SnO(2) using X-ray diffraction and subjecting the SnO to heat treatments between 300 °C < T < 600 °C in two different atmospheres, argon and air. The intermediary oxide that appears in the disproportionation process was identified as Sn(2)O(3). In an argon atmosphere, decomposition occurs in three stages: (1) a direct transformation of SnO to SnO(2), (2) the formation of some intermediary Sn(2)O(3) from SnO, and (3) the conversion of the Sn(2)O(3) to SnO(2) with the formation of metallic tin, Sn (l). When an atmosphere of air is used, however, a reaction occurs, concurrent with the decomposition reactions, that relates to the specific oxidation of the metallic tin produced in the course of the three process stages.