Dielectric relaxation properties of PbTiO₃-multiwalled carbon nanotube composites prepared by a sol-gel process

Dielectric composites fabricated by combining multi-walled carbon nanotubes (MWCNT) and PbTiO₃ (PTO) powder were prepared using a sol-gel process. Well-dispersed PTO powder with various volume ratios of MWCNT was compressed to form a pellet, and then silver electrodes were coated on both sides for electrical measurements. The PTO-MWCNT composite with 0.4 vol% MWCNT showed the highest dielectric constant (912 at 1 kHz), which is approximately 25 times larger than that (37 at 1 kHz) of a pure PbTiO₃ pellet. Furthermore, a strong frequency dependence of the dielectric constant in the low frequency range was shown for the PTO-MWCNT composites. Interfacial effects related to dielectric relaxation in composite materials were used to explain an observed increase of the dielectric constant near the percolation threshold.