Phase transformations induced by high electronic excitation in ion-irradiated Gd2(ZrxTi1−x)2O7 pyrochlores

The pyrochlore oxides (A2B2O7) exhibit a remarkable range of structural, physical, and magnetic properties related to their various chemical compositions. This article reports the phase transformations induced by high electronic excitation in pyrochlores of the Gd2(ZrxTi1−x)2O7 family irradiated with swift ions. The structural changes, investigated by using several analytical techniques (x-ray diffraction, Raman spectroscopy, and transmission electron microscopy), strongly depend on the chemical composition. The high electronic excitation along the ion trajectory results in the amorphization of ion tracks for Gd2Ti2O7 and Gd2TiZrO7, whereas a defective fluorite structure is formed in Gd2Zr2O7. Moreover, the results underline the existence of an electronic stopping power threshold of 6 keV/nm for amorphizable compounds and 10 keV/nm for Gd2Zr2O7, below which phase transformations do not occur. Finally, the study of the thermal recovery of irradiated pyrochlores provides the recrystallization temperature for amorphized samples and reveals differences in the recovery process which are related to the chemical composition.