Crack initiation patterns at electrode edges in multilayer ferroelectric actuators

This is the preprint of an article that will appear in Smart Materials and Structures (SMS)

Title: Crack initiation patterns at electrode edges in multilayer ferroelectric actuators

Authors: Amir Abdollahi and Irene Arias, Universitat Politecnica de Catalunya (UPC), Barcelona

Abstract:

In multilayer ferroelectric actuators, electrode edges are the main source
of fracture due to the generation of non-uniform electric fields in their vicinity.
The electric fields, in turn, induce incompatible strain fields and hence concentrated
stresses, which may cause the ceramic to crack. In this paper, the crack initiation
from the electrode edges is simulated using a phase-field model. This model is
based on variational formulations of brittle crack propagation and domain evolution in
ferroelectric materials. The simulation results show different crack initiation patterns
depending on the bonding conditions between the ceramic and electrode layers. Three
extreme conditions are considered, which are the fully cofired, partially cofired, and
separated layers. The crack initiation patterns can be either delimitation along the
electrode-ceramic interface or oblique cracking from the electrode into the material.
The calculations suggest a mechanism explaining the experimentally observed crack
branches near the electrode edges. The effects of the ceramic layer thickness and length
of the internal electrode on the crack initiation are also evaluated.