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Electric permittivity of reduced graphite oxide

Hong, Xinghua, Yu, Weidong, Chung, D.D.L.
Carbon 2017 v.111 pp. 182-190
capacitance, graphene, hydrazine, paper
The through-thickness electric permittivity (real part) of the solid part (53 vol%) of reduced graphite oxide (RGO) paper (100–300 μm thick, prepared by hydrazine reduction of modified-Hummers-method graphite oxide, GO) is 1130 (50 Hz), which is higher than that of the similarly tested parent GO (915, 50 Hz) and other carbons (31–124, 50 Hz). The high permittivity of RGO is attributed to the defects. Due to the conductivity of RGO, an insulating film between the specimen and an electrical contact is necessary during permittivity measurement using an RLC meter. Without the film, the measured capacitance is too high by 10–11 orders of magnitude, thus resulting in incorrectly high values of the permittivity. The relative permittivity 4 × 109 (20 Hz) reported by Sarkar et al. (2016) for similarly prepared RGO is therefore incorrect. The solid part of the RGO paper exhibits at 50 Hz in-plane conductivity 31 S/m, through-thickness conductivity 1.17 S/m, through-thickness relative permittivity (imaginary part) −4.2 × 108, through-thickness dielectric loss angle 90.0°, specific capacitance of the interface with an electrical contact 0.31 μF/m2, and areal resistivity of this interface 0.18 Ω cm2. The resistivity and specific capacitance of the RGO-contact interface are lower for RGO than GO.