STRUCTURAL STUDY OF ZR0.8SN0.2TIO4

The crystal structure of Zr0.8Sn0.2TiO4 has been investigated using ex tended X-ray absorption fine structure (EXAFS) spectroscopy, neutron p owder diffraction and Raman spectroscopy techniques. It possesses an o rthorhombic alpha-PbO2 type structure [space group Pbcn]. EXAFS spectr oscopy 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 Zr5T i7O24. Consistent with the EXAFS interpretation, an empirical analysis of the Raman spectra indicates that the tin ions prefer to be on tita nium sites. A superstructure is observed in Zr0.8Sn0.2TiO4 which is ca used by the non-stoichiometric nature of the sample. A small concentra tion of tin ions are probably in the reduced Sn2+ state, creating defe cts which undergo short-range ordering in the crystal.