ANALYSIS OF DOUBLE-LAYERED STRUCTURE OF SUBMICRON BATIO3 GRAINS USINGEQUIVALENT-CIRCUIT MODEL

Double layered structure of submicron BaTiO3 grains (0.1-0.6 mu m), in which the grain core is covered with a surface layer, has been analyz ed using the equivalent circuit model. The observed permittivity of si ntered pellets increases with increasing grain diameter. This agrees w ith a model in which the ferroelectric tetragonal core is covered with the paraelectric cubic surface layer. The best fit of this model to t he observed permittivity has shown that the; permittivity of the tetra gonal phase is 5900 and that of cubic phase is 90. Also the thickness of the cubic surface layer in the sintered pellet has been estimated t o be approximately 2 nm, which agrees well with that estimated from th e X-ray diffraction peak analysis.