Frequency‐Independent and Colossal Dielectric Permittivity of Platy Alumina/Few‐Layer Graphene Multilayered Composites. (27th February 2018)

• Record Type: Journal Article
• Authors: Choi, Ki‐Beom; Lee, Sung‐Min; Hwang, Jae‐yeol; Yoon, Dae Ho; Lee, Kyu Hyoung; Kim, Jong‐Young
• Is Part Of: Bulletin of the Korean Chemical Society. Volume 39:Number 4(2018)
• Page Start: 442
• Page End: 447
• Publication Date: 2018-02-27
• Subjects: Permittivity -- Dielectric relaxation -- Platy alumina -- Graphene -- Composite; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/bkcs.11405
• Languages: English
• ISSNs: 0253-2964

Abstract

Abstract : In this work, we investigated the dielectric property of layer‐structured Al2 O3 /few‐layer graphene (FLG) composite by high temperature impedance spectroscopic analysis. The sintered composites have highly enhanced permittivity (ε = 17.3) compared to pure platy alumina (ε = 7.3) with low dielectric loss (tanδ ~ 10 −3 ). Percolative permittivity of the composites exhibits almost frequency‐independent behavior at 1 Hz to 1 MHz even though the real permittivity was increased, compared to that of pure platy alumina. Such behavior can be explained by intervening dielectric interface between alumina and FLG based on multilayer filler model. After percolation threshold (FLG > 0.75 vol %), the permittivity is further enhanced up to ~260 (@1 kHz), which amounts to >35 fold increase, compared to pure platy alumina because of interfacial capacitance between FLG platelets and alumina. According to temperature‐dependent impedance analysis, a dielectric relaxation due to Al2 O3 /FLG interface is observed in the frequency range of 1 Hz to 1 kHz at high temperature (RT = 400°C) besides that due to Al2 O3 grains (>10 MHz). Real permittivity increases up to >20 000 at 400°C at low frequency, whereas dielectric loss remains as tanδ ~ 3 × 10 −4 . High temperature impedance analysis shows that the effect of interface between Al2 O3 and FLG is responsible for such dielectric relaxation at high temperature. Abstract : Authors are required to submit a graphic abstract for the Table of Contents that should give the reader a representative idea ofone of the following: A key structure, reaction, equation, concept, or theorem, etc., that is discussed in the manuscript. Upon reduction, the graphic should be no wider than 5.2 in. (13 cm) and no taller than 2 in. (5 cm).