X-ray diffraction and X-ray absorption spectroscopy studies of sol-gel-processed zirconium titanates

ZrTiO4 samples were prepared by using a conventional hydrolytic alkoxide so l-gel route, a nonhydrolytic method, an acetic acid modified route, and by the direct reaction of the binary oxides. The local structure in the gels a nd its evolution upon heating was followed using EXAFS and XANES, and the c rystallization of the products was examined using powder X-ray diffraction. All the solution-processed materials crystallized in the range 600-700 deg reesC. The crystalline materials formed at 700 degreesC showed no evidence of any long-range cation ordering. The EXAFS data indicated that all the am orphous ZrTiO4 samples produced using the solution routes contained zirconi um with a coordination number >6 and that the disordered crystalline ZrTiO4 contained six-coordinate zirconium. Both the XANES and EXAFS data showed t hat nearly all the amorphous ZrTiO4 samples contained titanium with a coord ination number of <6. The EXAFS data clearly indicated the presence of Zr-O -Ti links in the ZrTiO4 gel produced using the nonhydrolytic route. There w as also some evidence that the gel prepared using hydrolytic sol-gel chemis try contained Zr-O-Ti links.