Grain size effects on the dielectric constant of CaCu3Ti4O12 ceramics

The CaCu3Ti4O12 (CCTO) compound shows an unusually high and almost temperature independent dielectric constant at low frequencies. CCTO powders have been synthesized by an organic gel-assisted citrate process. The ceramic microstructure was optimized for a given sintering process. Both the grain size and density are shown to be maximum when PVA is introduced in powder before the complete formation of CCTO. A correlated increase of the dielectric constant is evidenced by impedance spectroscopy measurements. Results support the IBLC model proposed to explain the high dielectric constant of CCTO.