Multifunctional radiation shielding performance of hafnium-containing MAX-related borides: The impact of A-site chemistry and boron concentration

This study investigates the influence of A-site chemistry and boron concentration on the gamma-ray (γ-ray), neutron, and charged particle attenuation of a series of hafnium-containing MAX-related borides (Hf2SB, Hf2SeB, Hf2InB, Hf2TeB, Hf2PbB, Hf2BiB, Hf2InB2, Hf2SnB2, Hf3PB4, and Hf3SnB4) via systematic theoretical calculations. For γ-rays, efficiency is governed by a compositional trade-off between effective atomic number, density, and elemental composition: high atomic number (high-Z) Hf2BiB and Hf2PbB exhibited the highest calculated attenuation performance among the investigated MAX-related borides and showed lower half-value layer (HVL) values than pure lead (Pb) at selected photon energies, particularly around 2.5 MeV. Analysis showed that selected light-A-site compositions, particularly Hf2SB and Hf3PB4, maintain competitive γ-ray attenuation relative to binary HfB2 by preserving a high hafnium (Hf) fraction, although the relative ranking depends strongly on the photon-energy regime and attenuation parameter considered. For neutrons, performance was primarily driven by boron content. Among the investigated MAX-related borides, the boron-rich Hf3PB4 and Hf3SnB4 phases demonstrated the highest fast neutron removal cross sections, reaching up to 0.1647 cm-1, and exceeded the B4C benchmark value used in this study (0.141 cm-1). Notably, these phases also showed short-calculated ranges for protons and alpha particles, suggesting favorable heavy charged-particle stopping behavior associated with their relatively high light-element content. This trade-off identifies Hf3PB4 as the most balanced multifunctional candidate among the investigated compositions, combining strong neutron and heavy charged-particle attenuation with competitive γ-ray shielding, and highlights the potential of Hf-containing MAX-related borides for multifunctional radiation-shielding applications.