Response of nonstoichiometric pyrochlore composition Nd_1.8Zr_2.2O_7.1 to electronic excitations

In response of swift heavy ion (100 MeV I9+) irradiation, the irradiation-induced disordering in nonstoichiometric pyrochlore composition (Nd1.8Zr2.2O7.1) was compared to that of stoichiometric composition Nd2Zr2O7. Both compositions were prepared through auto gel-combustion followed by sintering under the identical conditions. Systematic analysis of the compositions before and after irradiation was performed with X-ray diffraction (XRD), Raman spectroscopy, and plane-view high-resolution transmission electron microscopy (HRTEM) techniques. Irradiation caused pyrochlore to amorphous phase transformation was observed in both compositions except the slower rate of amorphization in Nd1.8Zr2.2O7.1. The amorphization was achieved as a consequence of isolated disordered track overlapping at higher ion fluence with the estimated track diameter 2.73 +/- 0.05 and 3.46 +/- 0.30 nm for Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively, employing the framework of single-ion impact model to XRD results. HRTEM micrographs also revealed the less prevalence of irradiation-induced amorphization in Nd1.8Zr2.2O7.1 with the observed irradiation-induced modified track region composed of defect-rich pyrochlore structure, anion-deficient fluorite structure, and amorphous domains; with the diameter of 3.0 +/- 1.0 nm and 5.0 +/- 1.0 nm in Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively. The preexisting anion-deficient fluorite structure in Nd1.8Zr2.2O7.1 helps in its epitaxial growth as recovered structure from melted ion track during irradiation-induced rapid cooling.