Defect-Fluorite Gd2Zr2O7 Ceramics under Helium Irradiation: Amorphization, Cell Volume Expansion, and Multi-stage Bubble Formation

TL;DR

This study investigates how grain size affects radiation resistance in Gd2Zr2O7 ceramics under helium irradiation, revealing size-dependent amorphization, cell expansion, and bubble formation, with grain boundaries playing a protective role.

Contribution

It provides new insights into the size-dependent radiation response of Gd2Zr2O7 ceramics and highlights the critical role of grain boundaries in defect mitigation.

Findings

Cell volume expansion increases with grain size.

Amorphization fraction is size-dependent.

Nanograin ceramics show higher threshold He concentrations for bubble formation.

Abstract

Here, we report a study on the radiation resistance enhancement of Gd2Zr2O7 nanograin ceramics, in which amorphization, cell volume expansion and multi-stage helium (He) bubble formation are investigated and discussed. Gd2Zr2O7 ceramics with a series of grain sizes (55-221 nm) were synthesized and irradiated by 190 keV He ion beam up to a fluence of 5x10^17 ions/cm2. Both the degree of post irradiation cell volume expansion and the amorphization fraction appear to be size dependent. As the average grain size evolves from 55 to 221 nm, the degree of post irradiation cell volume expansion increases from 0.56 to 1.02 %, and the amorphization fraction increases from 6.8 to 11.1 %. Additionally, the threshold He concentrations (at. %) of bubbles at different formation stages and locations, including (1) bubbles at grain boundary, (2) bubble-chains and (3) ribbon-like bubbles within the grain, are all found to be much higher in the nanograin ceramic (55 nm) compared with that of the submicron sample (221 nm). We conclude that grain boundary plays a critical role in minimizing the structural defects, and inhibiting the multi-stage He bubble formation process.