Dielectric properties and energy storage performance of CCTO/polycarbonate composites: influence of CCTO synthesis route

摘要

This work explores the effect of CaCu3Ti4O12 (CCTO) synthetic route on CCTO/polycarbonate (PC) composite microstructure, low-field dielectric properties (epsilon(eff) and tan delta), and high-field polarization behavior. CCTO was synthesized via the traditional solid-state route and a wet chemical sol-gel route. PXRD, FE-SEM and BET analysis results show that sol-gel CCTO particles are 20 times smaller and have 20 times more surface area per gram than solid-state CCTO particles. Solution-blended 20 vol% sol-gel CCTO/PC composites have up to 12 times higher epsilon(eff) values than PC. Surprisingly, the permittivity enhancement due to the smaller sol-gel CCTO particles is not much more than that found using the larger solid-state CCTO particles. Sol-gel CCTO/PC composites show higher dielectric loss and specific conductivity than solid-state CCTO/PC composites, probably due to the presence of polyethylene glycol added as a dispersant in sol-gel CCTO synthesis. The CCTO introduces ferroelectric behavior to the composites, including significant remanent polarization, hysteresis, and energy dissipation. The stored and recovered energy densities in CCTO/PC are up to five times higher than PC at the same applied electric field, but the percentage energy loss reaches 70 %. CCTO/PC composites also have greatly reduced breakdown field strength compared to PC, so the composites' maximum stored energy density is much less than that of PC. Thus CCTO/PC composites are promising for applications requiring high epsilon(eff) values at low field strengths, but not as dielectrics for high density, pulse power energy storage.