Dramatic effect of multiwalled carbon nanotubes on the electrical properties of alumina based ceramic nanocomposites

We report recent work on electrical properties of multiwalled carbon nanotubes (MWNTs)/alumina composites. The composites with different contents of MWNTs were consolidated by spark plasma sintering and their temperature dependence dc conductivity was scrutinized in the temperature range from 5 to 300 K. The analysis of the temperature dependence of the conductivity suggests that for temperatures higher than 50 K, conduction can be ascribed to thermal fluctuation induced tunneling of the charge carriers through insulating barriers between MWNTs, while at temperatures below 50 K, the conduction can be attributed to three dimensional variable range hopping through MWNTs network in the alumina matrix. The frequency dependence of the conductivity was studied from 5 to 1.3 × 107 Hz. The universality of the ac conduction in MWNT/alumina composites was examined by construction of master curve.