Note. Antimony-121 Mössbauer study of the effects of calcination on the structure of tin–antimony oxides

Abstract

The formation of tin–antimony oxides by the calcination of gels produced by alkaline precipitation of tin(IV) and antimony(V) chlorides has been investigated by ¹²¹Sb Mössbauer spectroscopy. Calcination at 300 °C produces partially dehydrated solids in which some Sb^V is reduced to Sb^III. The subsequent transformation to blue poorly crystalline materials at 600 °C in which the cations occupy oxygen environments is associated with further dehydration and the initiation of thermally induced structural changes. Prolonged heating at 600 °C or short period calcination at high temperature is accompanied by the segregation of a separate Sb₂O₄ phase. The high concentration of Sb^III which accompanies calcination at 1 000 °C is associated with the formation of a monophasic solid solution of antimony in tin(IV) oxide in which the surface is enriched in antimony.