Structural study of Zr sub(0.8)Sn sub(0.2)TiO sub(4)

The crystal structure of Zr sub(0.8)Sn sub(0.2)TiO sub(4) has been investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy, neutron powder diffraction and Raman spectroscopy techniques. It possesses an orthorhombic alpha -PbO sub(2) type structure (space group Pbcn). EXAFS spectroscopy reveals that its zirconium ions possess 8-fold coordination as noted in Zr sub(5)Ti sub(7)O sub(24), while its tin ions possess 6-fold coordination. X-ray diffraction and EXAFS results indicate that Zr sub(0.8)Sn sub(0.2)TiO sub(4) exists in a structural state between that of high-temperature ZrTiO sub(4) and Zr sub(5)Ti sub(7)O sub(24). 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 Zr sub(0.8)Sn sub(0.2)TiO sub(4) which is caused by the non-stoichiometric nature of the sample. A small concentration of tin ions is probably in the reduced Sn super(2+) state, creating defects which undergo short-range ordering in the crystal.