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.