In-situ transmission electron microscopy study of electric-field-induced grain-boundary cracking in lead zirconate titanate

The field-driven in-situ transmission electron microscopy (TEM) technique was developed to examine micromechanisms of field-induced cracking in ferroelectric ceramics. The technique was constructed by combining a selectively deposited thin film electrode configuration with a modified hot stage to deliver a required electric voltage to a ferroelectric TEM specimen. Under cyclic electric fields, microcracks were found to initiate from pores at the triple junctions and propagate along the grain-boundary in a lead zirconate titanate (PZT) ceramic. Grain-boundary cavitation and coalescence of microcracks were directly observed for the first time during field-induced fracture of PZT at room temperature. The results suggest that dielectric breakdown of the grain-boundary phase was conducive to grain-boundary cavitation, and the crack growth followed the progressive accumulation of the cavity density with electric cycling.