Negative capacitance in (FeCoZr)–(PZT) nanocomposite films

Abstract

In this work, attention was focused on the inductive contribution to the real part of admittance G(T , f ) in (Fe 0.45 Co 0.45 Zr 0.10 ) x (PZT) (1−x) nanocomposite films deposited in a mixed argon-oxygen atmosphere. The observed G(x, f, T ) dependences for the films on the dielectric side of the insulator-metal transition demonstrated the negative capacitance (NC) effect that was maximal for the nanocomposites with 0.40 < x < 0.60, where the metallic FeCoZr nanoparticles were totally oxidized. The NC effect was explained by a specially developed model for the ac hopping conductance of the electrons between the fully oxidized nanoparticles embedded in the PZT matrix. In accordance with the model, under the determined conditions the observed structure of nanocomposites led to an increase in the hopping electron mean lifetime on nanoparticles and hence to the possibility of positive angles of the phase shifts θ and a proper NC (inductive-like contribution) effect.

Permittivity of a composite of cellulose, mineral oil, and water nanoparticles: theoretical assumptions

“…In the paper by Kołtunowicz et al (2013), a model of the hopping electron transfer has been presented for direct and alternating current.…”

“…As the experimental characteristics do not include such points, we have selected inflection points on the log e 0 in the function of log f curves to be used as reference points. In order to determine the inflection points, the frequency coefficient a(f) expressed by formula (Kołtunowicz et al 2013;Svito et al 2014):…”

Dielectric Properties of (CoFeZr)_x(PZT)100-xNanocomposites Produced with a Beam of Argon and Oxygen Ions

“…In case of less complex matrixes, for example (FeCoZr) x (Al 2 O 3 ) 100−x , percolation threshold of nanocomposites, which were sputtered with pure argon ions beam, amounts to around (54±2) at.% [11], and percolation threshold for nanocomposites sputtered with mixed argon and oxygen ions beam increases to value of around (78 ± 5) at.% [12]. Figure 1 shows the Arrhenius dependences on conductivity of lms annealed in temperatures from 398 K to 548 K. As is shown in this gure, derivative conductivity values from the temperature amounts to dσ dT > 0.…”

“…2). These conductivity dependences can be explained by use of model of hopping conductance on AC and DC, presented in papers [14,15]. Model predicts that after electron tunnelling from one neutral potential well created by metallic phase nanoparticle to another a dipole appears, therefore, increase of dielectric permittivity takes place.…”

Annealing of (CoFeZr)x(CaF2)100-xNanocomposites Produced by the Ion-Beam Sputtering in the Ar and O2Ambient

“…As early as in the course of the nanocomposite formation by the beam of argon and oxygen ions, that a layer of oxides of the metallic-phase metals forms on the surface of the nanoparticles [6]. It causes shifting of the percolation threshold to the area of higher metallic-phase contents x from 54 at.% for a beam of pure argon [3] up to 78 at.% for a beam of argon and oxygen [7]. Annealing in the atmospheric air can have intensifying eect on the mentioned phenomena as it causes diusion of oxygen into the nanocomposite lm.…”