Heavy-ion irradiation effects on structures and acid dissolution of pyrochlores

The temperature dependence of the critical dose for amorphization, using 0. 6 MeV Bi+ ions, for A(2)Ti(2)O(7) pyrochlores, in which A=Y, Sm, Gd and Lu, exhibits no significant effect of A-site ion mass or size. The room temper ature dose for amorphization was found to be similar to0.18 dpa in each cas e. After irradiation with 2 MeV Au2+ ions glancing-incidence X-ray diffract ion (XRD) revealed that each pyrochlore underwent an irradiation-induced st ructural transformation to fluorite in conjunction with amorphization. The effect of amorphization on the dissolution rates of fully dense pyrochlores , at 90 degreesC and pH 2 (nitric acid) varied from a factor of 10 to 15 in crease for Gd2Ti2O7 to none for Y2Ti2O7 Significant differences were observ ed in the A-site dissolution rates from the crystalline pyrochlores, indica ting differences in the manner in which the A-site cations are incorporated into the pyrochlore structure. These indications were supported by Raman s pectroscopy. Crown Copyright (C) 2001 Published by Elsevier Science B.V. Al l rights reserved.