X-ray photoelectron spectroscopy study of irradiation-induced amorphizatonof Gd2Ti2O7

The radiation-induced evolution of the microstructure of Gd2Ti2O7, an impor tant pyrochlore phase in radioactive waste disposal ceramics and a potentia l solid electrolyte and oxygen gas sensor, has been characterized using tra nsmission electron microscopy and x-ray photoelectron spectroscopy. Followi ng the irradiation of a Gd2Ti2O7 single crystal with 1.5 MeV Xe+ ions at a fluence of 1.7x10(14) Xe+/cm(2), cross-sectional transmission electron micr oscopy revealed a 300-nm-thick amorphous layer at the specimen surface. X-r ay photoelectron spectroscopy analysis of the Ti 2p and O 1s electron bindi ng energy shifts of Gd2Ti2O7 before and after amorphization showed that the main results of ion-irradiation-induced disorder are a decrease in the coo rdination number of titanium and a transformation of the Gd-O bond. These f eatures resemble those occurring in titanate glass formation, and they have implications for the chemical stability and electronic properties of pyroc hlores subjected to displacive radiation damage. (C) 2001 American Institut e of Physics.