Negative Permittivity Behaviors Derived from Dielectric Resonance and Plasma Oscillation in Percolative Bismuth Ferrite/Silver Composites

Abstract

Negative permittivity of materials can be obtained by plasma oscillation or dielectric resonance, but the relationship between these two negative permittivity behaviors has been neglected. Combining the advantages of two negative permittivity behaviors, the negative permittivity can be more tunable and is expected to realize epsilon-near-zero behavior. In this work, percolative bismuth ferrite/silver composites with different contents of Ag were successfully fabricated by a simple solid-state sintering method. With the addition of Ag, the Lorentz-like and Drude-like negative permittivity behaviors were successively observed in bismuth ferrite/silver composites. The reasons for the two types of negative permittivity behaviors are dielectric resonance and plasma oscillation, respectively. Further investigation revealed that the synergistic effect of dipole resonance and free electrons led to a change of resonance frequency, a decrease of magnitude, and a transition of two negative permittivity behaviors. Moreover, with the addition of Ag in percolative bismuth ferrite/silver composites, the electrical conductivity and thermal conductivity changed abruptly at a certain volume fraction, suggesting a percolation behavior.

Negative Capacitance and Intrinsic Ferroelectric Behavior in α-MoO3 Culminating as a Robust Piezoelectric Energy Harvester

“…58 Although the negative ε″ is not an intrinsic dielectric feature for material due to the Fabry−Perot or Mie resonance, it is an inherent physical for devices. 58,59 The capacitance trends with respect to increasing frequency are plotted in Figure 8d. The capacitance value oversaw a sharp decrease to crossover into the NC region and reached a saturation value of −3.25 pF in the region of 1−100 kHz and once again gradually increased and saturated again as it approached 50 MHz, just like it was observed in the frequency response of ε r ′.…”

“…Zhang et al have shown that this negative ε″ may originate from the magnetoelectric coupling effect where a transformation between magnetic energy and electric energy is instigated, in accordance with source-free Maxwell’s equation for electrodynamics under magnetoelectric coupling and the second law of thermodynamics . Although the negative ε″ is not an intrinsic dielectric feature for material due to the Fabry–Perot or Mie resonance, it is an inherent physical character for devices. , The capacitance trends with respect to increasing frequency are plotted in Figure d. The capacitance value oversaw a sharp decrease to crossover into the NC region and reached a saturation value of −3.25 pF in the region of 1–100 kHz and once again gradually increased and saturated again as it approached 50 MHz, just like it was observed in the frequency response of ε r ′.…”

Flexible MWCNT/PVA/Mn Ferrite/AC Metacomposites with Tunable Negative Permittivity for Low-Frequency Reflectors and Optical Sensors

“…The permittivity of a material plays a crucial role in various applications where different dielectric properties are required to fulfill specific needs. These dielectric properties, determined by the permittivity, vary depending on the desired application and the material’s ability to respond to electric fields. − Before Veselago proposed the theoretical possibility of negative refraction, almost all previous investigations concentrated on the positive permittivity while giving the negative permittivity less attention . Epsilon-negative materials have been shown to have a wide range of potential applications, including coil-free resonators, novel capacitors with high permittivity, negative capacitance field effect transistors, and high-power microwave filters …”