  A time domain finite element numerical study of impedance spectroscopy in
composite electroceramics is presented. The simulations take into account the
complexity of the realistic three dimensional granular structure including
grains and grain boundaries. Two types of finite elements are used to represent
the bulk (tetrahedrons) and the grain boundary (prisms) phases, which allow
using extremely high bulk to grain boundary ratios. Simulations at various
frequencies reveal a strong influence of the grain shape on the impedance data
of the sample, both at low and at high frequencies.
