Heavy-ion irradiation effects in Gd-2(Ti2-xZrx)O-7 pyrochlores

Gd-2(Ti2-xZrx)O-7 samples with 0 less than or equal to x less than or equal to 1.5 were single-phase and pyrochlore structured after sintering at 1600 degreesC in air. The Gd2Zr2O7 (x = 2) end member predominantly displayed a n anion deficient-fluorite structure. Raman spectroscopy indicated that the level of short-range fluorite-like disorder in the unirradiated Gd-2(Ti2-x Zrx)O-7 samples increased significantly as Zr was substituted for Ti, despi te the retention of a long-range pyrochlore structure for samples with 0 le ss than or equal to x less than or equal to 1.5. Glancing-incidence X-ray d iffraction indicated that pyrochlores with an ionic radii ratio r(A)/r(B) l ess than or equal to 1.52(x greater than or equal to 1.5) were transformed into a radiation resistant defect-fluorite structure after irradiation at r oom temperature with 2 MeV AU(2+) to fluence of 5 ions/nm(2). As the ionic radii ratio of the pyrochlore increased beyond r(A)/r(B) > 1.52, the defect -fluorite structure became increasingly unstable with respect to the amorph ous state under identical irradiation conditions. Crown Copyright (C) 2001 Published by Elsevier Science B.V. All rights reserved.