SnO2/SiO2and Sn/Sb-oxide/SiO2gel-derived composites. Part 1: Structural evolution from a Mössbauer study

✍ Scribed by G. Carturan; R. Ceccato; R. Campostrini; G. Principi; U. Russo

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 460 KB
• Volume: 5
• Category: Article
• ISSN: 0928-0707
• DOI: 10.1007/bf00486710

✦ Synopsis

SiO2/SnO2 = 80/20 gel samples are prepared from Si(OEt)4 and SnC14 or Sn(OEt)4. Samples doped with Sb oxide contents up to 4% are also studied. The evolution of these samples after treatment from room temperature to 1050°C is studied by n9sn Mrssbauer spectroscopy and X-ray analysis.

Results indicate that SnO2 separation depends on preparation method and Sn-or Sb-oxide precursors. In the case of Sn(OEt)4, hydrolysis is less complete than for SnC14 and thermal curing affords charcoal separation which leads to extensive reduction of Sn(IV) to Sn(II). Products obtained above 800°C are constituted by a well-defined SnO2 phase in the SiO2 matrix. Segregation of Sn(II) and subsequent oxidation to Sn(IV) are invoked to account for this final morphology. The presence of Sb oxide lowers Sn(IV) reduction and favours both SnO2 and SiO2 crystallization, via the occurrence of a Sn/Sb-oxide metastable phase observed in the 700-800°C interval.