Electroconductivity of Al2O3/graphene nanocomposite processed by SPS technique

Abstract

Electrical conductivity (σ), relative dielectric permittivity (εr) and dissipation factor (D) measured in graphene-alumina composites. Samples obtained by plasma spark sintering (SPS) from a mixture of raw powders: δ-alumina (36 nm average particle size) and graphene flakes (3 nm thickness and 2–3 μm length). Graphene content in samples was 0, 1 and 2% by weight. The study carried out for frequencies from 50 Hz to 100 kHz. Both c and εr were higher for Al2O3–2% graphene: up to 90 μS/m and 19 respectively; while alumina with 1% graphene showed similar values to the pure alumina samples: 50 μS/m to electrical conductivity and 16 to relative permittivity. The dissipation factor was similar in the three materials tested. D increased with the frequency, reaching high values (0.7) at 100 kHz. Composites with 1 and 2% graphene content showed a dissimilar dielectric behavior with the frequency. Alumina reflected a classical behavior of the permittivity dependence with the frequency. Graphene composites also show the same behavior at frequencies above 100 Hz. Below this frequency, the presence of graphene increases the relative permittivity to exceed that from pure alumina. The graphene content leads to rise of relative permittivity, which means easier polarizability.