EFFECTS OF PORE STRUCTURE ON DEPOLARIZING FACTOR AND DIELECTRIC-CONSTANT OF POROUS CERAMICS

A depolarizing factor for porous ceramics was investigated. The dielectric constant and depolarizing factor were derived as functions of porosity based on some pore models such as ellipsoidal, modified cube (or 3-0) and 3-3 models together with a new modified 3-3 model proposed here. The results were compared with experimental data on porous ceramics of PTZ (Pb(Zr, Ti)O-3) and TiO2. The depolarizing factor depends on inverse dielectric constant of the constituent substance, and is not always proportional to porosity p, in contrast to the prediction based on the ellipsoidal model. In addition, the depolarizing factor is highly dependent on pore structure of ceramics and can only be predicted by the modified cube model and the modified 3-3 model under the assumption of appropriate pore shape factors.