Vibrational modes in La2Zr2O7 pyrochlore irradiated with disparate electrical energy losses*

Abstract

Polycrystalline samples of La2Zr2O7 pyrochlore are irradiated by different energetic heavy ions to investigate the dependence of the vibrational mode variations on the irradiation parameters. The applied electronic energy loss (dE/dx)e increases from about 5.2 keV/nm to 39.6 keV/nm. The ion fluence ranges from 1 × 1011 ions/cm2 to 6 × 1015 ions/cm2. Vibrational modes of irradiated pyrochlore are analyzed by using Raman spectrum. Infrared active modes F1u at 192, 308, and 651 cm−1 appear in Raman spectra, and the F2g band at 265 cm−1 rises up due to the irradiation by 200-MeV Kr ions with (dE/dx)e of 16.0 keV/nm. Differently, for the pyrochlore irradiated by 1750-MeV Bi ions with (dE/dx)e of 39.6 keV/nm, in spite of the appearance of infrared active mode F1u 651 cm−1, the amorphous structure occurs according to the vibrational mode variations of pyrochlore irradiated at higher ion fluences. Amorphous tracks are observed in the samples, which confirm the occurrence of pyrochlore–amorphous transition in pyrochlore irradiated with (dE/dx)e of 39.6 keV/nm.