Electrical heterogeneity in CaCu₃Ti₄O₁₂ ceramics fabricated by sol-gel method

Using tetrabutyl titanate, calcium nitrate and copper nitrate, a gel of these compounds was obtained at room temperature which on subsequent heat treatments led to CaCu₃Ti₄O₁₂ (CCTO) powder at 900 ^{{ring operator}}C for 1 h. On sintering further at 1060 ^{{ring operator}}C for 48 h, the dielectric constant of CCTO ceramics is above 35 000 at 1 kHz, and it displays a good tune behavior. Impedance spectroscopy on CCTO ceramics demonstrates that they are electrically heterogeneous and consist of semiconducting grains with insulating grain boundaries. The dc bias experiment demonstrates clearly that the grain boundary response is consistent with a Schottky barrier response. Therefore, CCTO ceramics display an internal barrier layer capacitor (IBLC) behavior.