Direct observations of changes in ferroelectric domain configurations around the indentation and ahead of the crack front in soft-doped PZT

Abstract

The indentation response of polycrystalline soft doped-lead Zirconate Titanate (PZT) with varying ferroelectric domain configurations is investigated using nano and micro indentation. The as-poled (AP) PZT samples are selectively annealed at below and above the Curie temperature, Tc, to obtain different ferroelectric domain configurations. In the fully depoled state (with completely random ferroelectric domain configurations), PZT exhibit higher hardness, H (∼ 40%) as compared to AP PZT (where ferroelectric domains are highly ordered). Severe cracking is observed at the imprint corners at high indentation loads and ferroelectric domain configurations are visualized in the vicinity and ahead of the indentation crack using piezoresponse force microscopy. The ferroelectric domains remain fully plastic in the regions from where the crack has propagated and just ahead of the crack, while farther from the indentation crack, they are elastic. The indentation fracture toughness, KICi values computed from the cracks emanated from imprint corners indicate that ferroelectric domain configurations also influence toughening behavior of PZT. The results are rationalized using remnant strain, εr and converse piezocharge coefficient, d33* measured around the indentation crack. This work highlights the new pathways to tailor strength and toughness of PZTs. © 2021 Acta Materialia Inc.