Investigation of local structure and phase recovery in an irradiated Nd2Zr2O7 pyrochlore

Abstract

The ordering and disordering processes significantly impact the physicochemical properties of complex oxides when they are subjected to severe conditions such as high temperature, high pressure, or ion irradiation. Therefore, it is necessary to have a profound comprehension of the kinetics linked with cation ordering and disordering to customize the properties of materials for extreme environmental applications. This study investigates the impact of local atomic order on radiation response and structural stability as well as phase recovery of the Nd₂Zr₂O₇ pyrochlore when subjected to ion irradiation. X-ray absorption spectroscopy was performed on the Nd₂Zr₂O₇ pyrochlore before and after irradiation with 100 MeV I⁷⁺ ions at fluences of 1 × 10¹³ ions/cm² and 5 × 10¹³ ions/cm². The significant changes in the Nd-L₃ and Zr-K edges of X-ray absorption near edge structure (XANES) spectra confirm strong local distortions and modifications in the short-range ordering upon irradiation. Extended X-ray absorption fine structure (EXAFS) data reveal that the different local coordination environments of Nd and Zr cationic shells support the phase transformation as observed by XRD. In addition, phase recovery studied by in situ thermal annealing (300–1000 °C) using synchrotron X-ray diffraction revealed the thermal recovery of the crystalline phase, but the pyrochlore superstructure was not detected even upon annealing at a high temperature of 1000 °C. The findings of this study demonstrate that the local electronic structure has a profound influence on the structural stability of complex oxides, thus providing a critical factor for regulating the functional properties of these materials.