Role of domain configurations on the mechanistic modelling of indentation size effects (ISE) in nanohardness of hard and soft PZT piezoceramics

Abstract

The intrinsic microstructural length scales of piezoelectric materials (e.g. grain size, nature of the domain and their orientations) spans from micron to nanoscale have a pronounced influence on the electromechanical behaviour. Of all these microstructural features, domain configurations particularly found to control the nanomechanical properties which can be tailored using domain engineering techniques. Keeping this in view, we investigated the effect of different domain configurations on the indentation size effects (ISE) in nanohardness of polycrystalline hard and soft lead zirconate titanate (PZT). The state of different domain configurations in hard and soft PZT is achieved by annealing the poled specimens slightly below and above the Curie temperature (Tc). Nanoindentation experiments at different indentation sizes are performed to evaluate the proposal of ISE. Further, the size-dependence in nanohardness is analyzed using the classical Meyer’s law, the Hays-Kendall (H–K) model, the elastic recovery (ER) approach, the proportion specimen resistance (PSR) model and the modified PSR (MPSR) model. The results revealed that all the mechanistic models show excellent fitting of nanoindentation data and size-dependence in nanohardness is found to be sensitive to the domain configurations. The Meyer’s law and H–K approach quantifies the ISE in both the PZT but do not provide any significant understandings about the origins of ISE. The PSR and MPSR models demonstrated that besides the domain configurations, size-dependence in nanohardness in piezoceramics could also be attributed to (i) material-dependent constants and (ii) surface artefacts. The true hardness values obtained from the ER, PSR and MPSR models are similar to each other due to the similar attributes in fitting the nanoindentation data.