Transmission Electron Microscopy at Grain Boundaries of PTC-Type BaTiO3 Ceramics

Transmission electron microscopy of the grain boundaries of Ti-rich semiconducting PTC-type BaTiO₃ ceramics is described. At a width of 2 to 10 nm, there were no indications of intergranular second-phase layers covering the grains. Second phase was segregated only at the contacts of three or more grains; electron diffraction confirmed the amorphous structure of this phase. Observed ferroelectric domains at the grain boundaries do not indicate a PTC-specific orientation of ferroelectric domains due to the negative grain surface charge.