Temperature dependence of the radiation tolerance of nanocrystalline pyrochlores A2Ti2O7 (A = Gd, Ho and Lu)

Abstract

A potentially enhanced radiation resistance of nanocrystalline materials, as a consequence of the high density of interfaces and surfaces, has attracted much attention both to understand the fundamental role of these defect sinks and to develop them for high-radiation environments. Here, irradiation response of nanocrystalline A 2 Ti 2 O 7 (A = Gd, Ho and Lu) pyrochlore powders with grain sizes of 20-30 nm was investigated by 1-MeV Kr 2+ ion bombardment. In situ transmission electron microscopy (TEM) revealed that the critical amorphization fluence for each nanocrystalline compound at room temperature was greater than that for their coarsegrained counterparts, indicating an enhanced amorphization resistance. The effect of temperature on the irradiation response of one of these compounds, nanocrystalline Lu 2 Ti 2 O 7 , was further examined by performing ion irradiation at an elevated temperature range of 480 to 600 K. The critical amorphization temperature (T c) was found to be noticeably higher in nanocrystalline Lu 2 Ti 2 O 7 (610 K) than its coarse-grained counterpart (480 K), revealing that nanocrystalline Lu 2 Ti 2 O 7 is less resistant to amorphization compared to its coarse-grained phase under high temperatures. We interpret these results with the aid of atomistic simulations. Molecular statics

Structural evolution of Lu2‐xCexTi2O7 pyrochlores under 400 keV Ne irradiation

“…At the last stage, some nanocrystalline pyrochlores formed from the amorphous regions at a dose of 1.854 dpa (Figure 3D). This radiation‐induced recrystallization process has been observed in many complex ceramic materials 36,38,43,46 . For example, an ion beam‐induced amorphous‐to‐tetragonal phase transformation was found in ZrO 2 43 .…”

Role of ion species in radiation effects of Lu2Ti2O7 pyrochlore

“…It should be noted that, in our study, Ne 2+ irradiations were performed at cryogenic temperature (~77 K), and Ar 11+ and Xe 26+ irradiations were performed at room temperature (~293 K). Our recent study [43] has demonstrated that the amorphization dose of Lu 2 Ti 2 O 7 is a constant at low irradiation temperature range (0-400 K), and increases rapidly with increasing temperature at high temperature range (> 400 K), which is also confirmed by Lian's results [10]. Therefore, if the Ne 2+ irradiations were carried out at room temperature (same as the Ar 11+ and Xe 26+ cases) on Lu 2 Ti 2 O 7 , the threshold amorphization dose would be equal to (or maybe greater than) that obtained in present cryogenic case.…”

“…where G gb is the Gibbs free energy of grain boundaries, G pd is the Gibbs free energy of irradiation induced point defects and G pt is the Gibbs free energy barrier for the phase transition. In this work, all Lu 2 Ti 2 O 7 samples were synthesized through the conventional solid-state method and possess similar grain size of approximately 10 m [43], at which the influence of grain boundary is rather weak and can be ignored. We thereby should only consider G pd here.…”

Synthesis and in situ ion irradiation of A-site deficient zirconate perovskite ceramics

“…T c is dened as the temperature at which the rate of damage induced equals the rate of recovery from damage under specic irradiation conditions. As previously implemented by various groups, 37,62,63,[67][68][69][70][71][72][73][74][75][76] values of T c were calculated using a nonlinear least squares renement of eqn (1) using several models that can be accessed elsewhere. 77,78…”