Heavy-ion irradiation effects in Gd2(Ti2−xZrx)O7 pyrochlores

Gd2(Ti2−xZrx)O7 samples with 0⩽x⩽1.5 were single-phase and pyrochlore structured after sintering at 1600°C in air. The Gd2Zr2O7 (x=2) end member predominantly displayed an anion deficient-fluorite structure. Raman spectroscopy indicated that the level of short-range fluorite-like disorder in the unirradiated Gd2(Ti2−xZrx)O7 samples increased significantly as Zr was substituted for Ti, despite the retention of a long-range pyrochlore structure for samples with 0⩽x⩽1.5. Glancing-incidence X-ray diffraction indicated that pyrochlores with an ionic radii ratio rA/rB⩽1.52(x⩾1.5) were transformed into a radiation resistant defect-fluorite structure after irradiation at room temperature with 2 MeV Au2+ to a fluence of 5 ions/nm2. As the ionic radii ratio of the pyrochlore increased beyond rA/rB>1.52, the defect-fluorite structure became increasingly unstable with respect to the amorphous state under identical irradiation conditions.