STRUCTURAL STUDY OF ZR0.8SN0.2TIO4

The crystal structure of Zr0.8Sn0.2TiO4 has been investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy, neutron powder diffraction and Raman spectroscopy techniques. It possesses an orthorhombic alpha-PbO2 type structure [space group Pbcn]. EXAFS spectroscopy reveals that its zirconium ions possess 8-fold coordination as noted in Zr5Ti7O24, while its tin ions possess 6-fold coordination. X-ray diffraction and EXAFS results indicate that Zr0.8Sn0.2TiO4 exists in a structural state between that of high-temperature ZrTiO4 and Zr5Ti7O24. Consistent with the EXAFS interpretation, an empirical analysis of the Raman spectra indicates that the tin ions prefer to be on titanium sites. A superstructure is observed in Zr0.8Sn0.2TiO4 which is caused by the non-stoichiometric nature of the sample. A small concentration of tin ions are probably in the reduced Sn2+ state, creating defects which undergo short-range ordering in the crystal.