ION-BEAM MODIFICATION OF GD2TI2O7

Irradiation of Gd2Ti2O7 With 3 MeV Ar+ ions results in expansion of the unit cell volume and irradiation-induced amorphization. The damage cross section for amorphization determined from X-ray diffraction data is 0.023 nm2. Transmission electron microscopy and electron diffraction confirm the irradiation-induced amorphous character at high fluences. Raman spectroscopy indicates a decrease in scattered intensity and an increase in linewidth with fluence for the principal vibrational modes, consistent with increasing irradiation-induced disorder. The wave number of the most intense Raman peak at approximately 310 cm-1 (attributed to the O-Gd-O bending mode) decreases with fluence, indicating a change in bond angle. The increase with fluence in the wave number of the Raman peak at approximately 515 cm-1 (attributed to the Gd-O stretching mode) suggests a decrease in this bond length. At intermediate fluences, a forbidden peak at approximately 765 cm-1 becomes slightly activated by irradiation-induced disorder on the cation sites.