Investigation of the dielectric and optoelectronic properties of Nd³⁺-substituted bismuth ferrite ceramics in THz/far-infrared region

The real part of the dielectric permittivity of bulk ceramic ferroelectric of composition Bi_1−xNd_xFeO₃ (x = 0, 0.15, 0.2), synthesized by solid-state route, was characterized in the frequency range 0.1–3.5 THz using time-domain Tera-Hertz spectroscopy, and the effect of Nd³⁺ concentration on the Terahertz (THz) properties of polycrystalline BiFeO₃ (BFO) was investigated and is being reported for the first time. A partial transformation in the rhombohedral structural symmetry of BiFeO₃ was noticed with increasing Nd³⁺ % concentration. With increasing Nd³⁺ concentration, a gradual increase in the THz signal strength has been observed indicating a reduction in losses. For the first time, the refractive index and absorption coefficients of Bi_1−xNd_xFeO₃ (x = 0.0, 0.15, 0.20) samples were measured in the THz reflection mode, and the sample with higher Nd concentration was found to be more stable in terms of refractive index and absorption coefficient. The sample with x = 0.2 has the highest dielectric value (~ 4.5) at 3.5 THz radiation, which could have potential for THz applications. The detected temporal and spectral THz profiles of Bi_1−xNd_xFeO₃ (x = 0, 0.15, 0.2) bulk ceramic have shown exceptional stability in the frequency range studied.