Study of Negative Permittivity in Nanosized LaNiO<sub>3</sub> for Electromagnetic Interference Shielding: A Modified Drude Model Approach
Tarun Katheriya, Gurudeo Nirala, Shail Upadhyay
Abstract
Addressing the growing concern of electromagnetic (EM) pollution requires the development of advanced electromagnetic interference (EMI) shielding materials. This study investigates the epsilon-negative (ENG) behavior of nanosized LaNiO 3, highlighting its potential as a reflective shield for EMI and as an alternative to conventional metal-based composites in stealth and shielding applications. LaNiO 3 was synthesized by the sol–gel method, and its phase purity was confirmed via X-ray diffraction. Electrical characterization revealed consistent ENG behavior [ε r ′ ∼ (22.32 ± 0.11) × 10 6 ] and metallic conductivity (σ total ∼ 131 S/m) across 100 Hz to 1.5 MHz and up to 300 °C. The Drude model was initially applied to fit the experimental data; however, a significant mismatch between the theoretical model and the experimental results encouraged us to refine the theoretical approach by incorporating a term for displacement current, which had been neglected in the original Drude model. By fitting the modified Drude model to the experimental data points, we calculated the plasma frequency [ω p ∼ (3.09 ± 0.46) GHz] and damped frequency (ω τ ∼ 1.57 MHz). Impedance studies showed a negative phase angle (φ) and an upward trend in the Nyquist plot ( Z″ vs Z′ ), demonstrating an inductive nature for LaNiO 3 . Microwave measurements demonstrated a shielding effectiveness (SE) of ∼33 dB, primarily due to reflection resulting from impedance mismatch. The findings demonstrated that LaNiO 3 could be a promising candidate for EMI shielding in reflection mode.