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

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This work explores the effect of CaCu3Ti4O12 (CCTO) synthetic route on CCTO/polycarbonate (PC) composite microstructure, low-field dielectric properties (εeff and tan δ), 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 εeff 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 εeff values at low field strengths, but not as dielectrics for high density, pulse power energy storage.