Evidence of improved tolerance to electronic excitation in nanostructured Nd2Zr2O7
Saurabh Kumar Sharma, V. Grover, Rakesh Shukla, Abid Hussain, Ambuj Mishra, Ramcharan Meena, P. K. Kulriya
Abstract
Grain size driven effects on electronic excitation-induced structural modifications have been investigated in nanocrystalline (NC) Nd2Zr2O7 on irradiation with 100 MeV iodine ions. Characterizations have been performed with in situ x-ray diffraction, Raman spectroscopy, and plane-view high-resolution transmission electron microscopy techniques. NC-powders of Nd2Zr2O7 were synthesized by auto gel-combustion and sintered at different temperatures to obtain different grain-sized samples. XRD analysis of the smallest grain-sized sample reveals the highest order–disorder transition (from pyrochlore to a more radiation-resistant phase; anion-deficient fluorite) rate at initial ion fluences followed by least amorphization at higher ion fluences. A strong correlation of the transformation build-up with the double ion impact model confirms the two step amorphization process in NC-Nd2Zr2O7 with the disordered anion-deficient fluorite structure as an intermediate phase. TEM result supports the formation of circular ion track consisting of randomly distributed regions (anion-deficient fluorite structure and amorphous regions), surrounded by a microstrain induced defect-rich pyrochlore superstructure. Lesser ordering at cationic sites and a relatively larger number of grain boundaries are responsible for the highest radiation tolerance exhibited by the smallest grain-sized sample. The present study reports a relatively higher radiation stability of NC-ternary pyrochlore oxide, Nd2Zr2O7, with a grain size of a few tens of nm, which establishes its application as a potential inert matrix for nuclear applications.