Critical Behavior of the Dielectric Constant of a Random Composite near the Percolation Threshold

Although most insulators are expected to undergo insulator to metal transition on lattice compression, tetrahedral semiconductors Si, GaAs and InSb can become metallic on compression as well as by expansion. We focus on the transition by expansion which is rather peculiar; in all cases the direct gap at Γ point closes on expansion and thereafter a zero-gap state persists over a wide range of lattice constant. The solids become metallic at an expansion of 13% to 15% when an electron Fermi surface around L-point and a hole Fermi surface at Γ-point develop. We provide an understanding of this behavior in terms of arguments based on symmetry and simple tight-binding considerations. We also report results on the critical behavior of conductivity in the metal phase and the static dielectric constant in the insulating phase and find common behavior. We consider the possibility of excitonic phases and distortions which might intervene between insulating and metallic phases.

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Characterization of percolation behavior in conductor–dielectric 0-3 composites

Journal of Advanced Dielectrics ◽

10.1142/s2010135x14500350 ◽

2014 ◽

Vol 04 (04) ◽

pp. 1450035 ◽

Cited By ~ 9

Author(s):

Lin Zhang ◽

Patrick Bass ◽

Zhi-Min Dang ◽

Z.-Y. Cheng

Keyword(s):

Dielectric Constant ◽

Percolation Threshold ◽

Frequency Dependence ◽

Experimental Results ◽

Effective Dielectric Constant ◽

Filler Concentration ◽

Percolation Behavior ◽

The Matrix ◽

The Relationship

The equation ε eff ∝ (ϕc - ϕ)-s which shows the relationship between effective dielectric constant (εeff) and the filler concentration (φ), is widely used to determine the percolation behavior and obtain parameters, such as percolation threshold φc and the power constant s in conductor–dielectric composites (CDCs). Six different systems of CDCs were used to check the expression by fitting experimental results. It is found that the equation can fit the experimental results at any frequency. However, it is found that the fitting constants do not reflect the real percolation behavior of the composites. It is found that the dielectric constant is strongly dependent on the frequency, which is mainly due to the fact that the frequency dependence of the dielectric constant for the composites close to φc is almost independent of the matrix.

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Fluoro-polymer functionalized graphene for flexible ferroelectric polymer-based high-k nanocomposites with suppressed dielectric loss and low percolation threshold

Nanoscale ◽

10.1039/c4nr03957b ◽

2014 ◽

Vol 6 (24) ◽

pp. 14740-14753 ◽

Cited By ~ 111

Author(s):

Ke Yang ◽

Xingyi Huang ◽

Lijun Fang ◽

Jinliang He ◽

Pingkai Jiang

Keyword(s):

Dielectric Constant ◽

Dielectric Loss ◽

Percolation Threshold ◽

High Dielectric Constant ◽

Functionalized Graphene ◽

Ferroelectric Polymer ◽

Flexible Polymer ◽

High K ◽

High Dielectric

Fluoro-polymer functionalized graphene was synthesized for flexible polymer-based nanodielectrics. The resulting nanocomposites exhibit high dielectric constant, suppressed dielectric loss and low percolation threshold.

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