Microstructural effects on conductivity in donor doped BaTiO3

The relationship between domain morphology, grain boundary structure, dopant distribution and the effect on conductivity in lightly donor doped barium titanate was characterized using SEM and TEM. The compositional distribution and the structural relationship between adjacent domains were determined using the convergent beam electron diffraction technique. Only 90° a-a type head-to-tail domain structures were found. HREM images of grain boundary regions in annealed samples, in which domains are common to the boundary (25-35% of total boundary), show lattice coherency and depict electronic pathways. Domain configuration near and across grain boundaries contribute to the observed resistivity differences found between samples of varying heat treatment histories. Conduction in the ferroelectric state is modeled as a percolation of conducting electrons along mutually interacting domain pathways. Annealed samples result in an inhomogeneous grain boundary, where only a limited number of grain boundaries and grain boundary regions control electron flow.

Keywords:

• Barium titanate
• domain structure
• donor doping