Experimental & numerical investigation of electromechanical response of PMN-PT single crystals and porous PMN-PT

Abstract

The relaxor ferroelectric materials such as Pb(Mg1/3Nb2/3)O3 PbTiO3 (PMN-PT) exhibit excellent piezoelectric coupling coefficient (~1100 2500 pC/N), ultrahigh electromechanical coupling (~88 93%), and electrically induced strains (~0.4% 1.7%), which makes them an attractive choice for designing high-performance sensors and actuators for various applications like aerospace, defense, acoustic, and biomedical industries. The devices made of these materials are often subjected to contact forces which may lead to domain switching/phase-transformation (Schneider et al., 2005), and nucleation of surface cracks (Szutkowska), resulting in change in electromechanical properties and hence affecting the desired performance. This has encouraged the researchers to study the indentation response of these materials. The indentation experiments on single crystals of relaxor ferroelectric materials such as PZN-PT, PIN-PMN-PT and PMN-PT showed reduction in hardness with indentation load/depth which is referred to as indentation size effect (ISE) (Jin et al. 2008; Man et al., 2020; Zhang et al., 2020; Joseph et al. 2022). Though the mechanistic reasons for ISE in these materials are not well explained, it has been hypothesized by few authors that ISE is caused by increase in the resistance offered to the indenter by the inner layers of the material with enhancement in load (Jin et al., 2008). However, it is not clear why and how the hardness was higher at lower indentation load.