On the formation of M²⁺ -Sb³⁺ -alkoxide precursors and sol-gel processing of M-Sb oxides with M = Cr, Mn, Fe, Co, Ni, Cu and Zn

Abstract

Binary alkoxide complexes of compositions close to MSb(OEt)₅, with M = Mn, Fe, Co and Ni, have been prepared and characterized by their i.r. and u.v.-VIS spectra, while Cr, Cu and Zn do not form similar ethoxide complexes with Sb(OEt)₃. The Mn and Fe complexes must be prepared in inert atmosphere as they are very easily oxidized. The Fe complex is metastable and decomposes within a few hours. The Co complex can only be prepared in the presence of acetonitrile. X-ray amorphous gels were formed upon hydrolysis of solutions containing M to Sb species in the ratio 1∶2 for M = Mn, Fe, Co and Ni. The gels consisted of agglomerated particles of sizes from 75 to 300 nm. The decomposition of the gels in air and in nitrogen has been monitored by means of thermogravimetric measurements. Samples of heated gels were quenched from various temperatures in the region 50–950°C, and the formed oxides were characterized by their X-ray powder patterns and by their infrared spectra. At 950 °C MSb₂O₆ was formed in air, while in nitrogen MSb₂O₄ (M = Mn, Co and Ni) was formed at intermediate temperatures. At higher temperatures the latter compound decomposed and Sb₂O₃ sublimated.