Experimental investigation on the role of Bi³⁺ composition in structural, elastic, and radiation shielding properties of multifunctional cobalt-nickel nanoferrites

Abstract

The growing demand for effective radiation shielding materials has led to the exploration of alternative options to conventional materials, such as lead (Pb), which are heavy, toxic, and expensive. In this study, bismuth-doped nickel cobalt nanoferrites (Ni_0.5Co_0.5Bi_xFe_2-xO₄, with x = 00, 0.05, 0.10, 0.15, and 0.2 %) were synthesised via the solution combustion method. The effect of Bi composition in XRD analysis revealed a single-phase cubic spinel structure for low Bi compositions (x ≤ 0.05) and a dual-phase structure with α-Bi₂O₃ at higher doping levels (x ≥ 0.1). FTIR spectroscopy identified vibrational modes and band shifts attributed to lattice strain induced by Bi doping. The elastic properties, such as bulk modulus (B), rigidity modulus (G), Young’s modulus (Y), and Poisson’s ratio (σ) of the developed nanoferrites were studied with varying Bi composition. Young’s modulus showed a gradual variation between 195.26 GPa to 191.39 GPa, further supporting the idea of reduced elastic stiffness with increasing Bi composition. Additionally, the radiation shielding performance of these nanoferrites was experimentally evaluated using a NaI(Tl) detector and gamma sources (¹³³Ba, ¹³⁷Cs, ²²Na, and ⁶⁰Co). The mass attenuation coefficients, linear attenuation coefficients, half-value layer, tenth-value layer, mean free path, effective atomic number, and fast neutron removal cross-sections were computed using Phy-X/PSD software for various gamma energies. Experimental mass attenuation coefficients of nanoferrites (NCBFO-00 to NCBFO-0.20) increased from 0.0759 to 0.0797 cm²/g at 0.662 MeV. Among all the samples, the highest Bi-doped nanoferrites (NCBFO-0.20) demonstrated superior radiation shielding performance, making it a promising candidate for radiation protection applications.