Structural and compositional effects on the electronic excitation induced phase transformations in Gd2Ti2-yZryO7 pyrochlore

The isometric pyrochlore structure type A(2)B(2)O(7) possesses a wide range of technological applications such as electrolytes in solid oxide fuel cell, thermal barrier coating, and nuclear waste form for actinides incorporation. Pyrochlore series Gd2Ti2-yZryO7 with y = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 was prepared using standard solid-state method. X-ray diffraction along with SEM studies was carried out to investigate the effect of Zr content on microstructure and the swift heavy ion irradiation-induced effects on the structural integrity of Gd2Ti2-yZryO7 pyrochlore family. Rietveld refinement showed a systematic increase in the lattice parameter on increasing the value of y in Gd2Ti2-yZryO7 and an abrupt enhancement in the value of the O-48f positional parameter at y > 1.6. The intensity of superstructure peaks gradually decreases in the X-ray diffraction pattern on increasing the Zr content, which indicates the transformation from the ordered pyrochlore structure to disordered anion-deficient fluorite structure. On irradiation with swift heavy ion (120 MeV Au+9), the compositions with y = 0.0 and 0.4 were completely amorphized and the composition with y = 0.8 and 1.2 partially amorphized whereas no sign of amorphization was observed in the Zr rich (y = 1.6 and 2.0) compositions. The composition with y >= 1.6 retains its crystallinity even at higher ion fluence of 1 x 10(14) ions/cm(2). These results are explained on the basis of the ratio of cationic radii r(A)/r(B) and in turn the 'x' parameter of 48f oxygen. (C) 2020 Elsevier B.V. All rights reserved.