Abstract: Control rod materials for nuclear reactors require both high neutron absorption efficiency and good mechanical properties. However, conventional materials cannot withstand the harsh service environments. To address this challenge, a high-entropy design strategy was adopted to develop novel ceramic composites. Herein, low-entropy GdAlO₃-Gd₂Zr₂O₇ (GAP-GZO) and high-entropy REAlO₃-RE₂Zr₂O₇ (REAP-REZO, RE=Nd, Sm, Gd, Eu, Dy) ceramic composites were prepared by pressureless sintering. Microstructural characterization shows that both sintered ceramics exhibit well-defined dual-phase microstructures with no amorphous phase. Compared with GAP-GZO, the high-entropy REAP-REZO exhibits a more uniform phase distribution, finer grains, and higher density. Mechanical testing shows that REAP-REZO has higher Vickers hardness and an approximately 21% improvement in fracture toughness compared to GAP-GZO. This enhancement is attributed to a combination of toughening mechanisms, including crack deflection, crack bridging, crack bifurcation, and micro-pore toughening. Regarding neutron absorption, Monte Carlo N-Particle (MCNP) simulations demonstrate that REAP-REZO exhibits excellent and stable neutron absorption across a wide energy spectrum, especially for thermal neutrons. A 150-mm thick REAP-REZO sample achieves a neutron absorption rate of 93.7% against the 2.45 MeV neutron source. This work demonstrates that the high-entropy ceramics design can improve both mechanical properties and neutron absorption capability, providing an alternative route for developing advanced generation control rod materials.

Key words: high-entropy ceramic, neutron absorption capability, fracture toughness, control rod