Electret state in Bi4Ti3O12 ceramics

The effect of thermal treatment atmosphere (argon, air or oxygen) on the electret behavior of bismuth titanate (Bi4Ti3O12) ceramics was investigated. Polycrystalline ferroelectric ceramics were prepared by reactive liquid phase sintering. Sintered samples were polarized applying an electric field, Ep = 1 MV m−1 at 100 °C for 60 min. Effective surface density, σeff of free charges was determined by compensation voltage measurements. Thermally treated samples in oxygen atmosphere exhibit a significant decrease of σeff while those treated in argon exhibit an increase of σeff accompanied by the improvement in stability of electret charge. In all cases homocharge with a time independent sign was obtained.