Vibrational modes in La₂Zr₂O₇ pyrochlore irradiated with disparate electrical energy losses

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 F_1u at 192, 308, and 651 cm^-1 appear in Raman spectra, and the F_2g 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 F_1u 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.