Investigations of ferroelectric polycrystalline bulks and thick films using piezoresponse force microscopy

In recent years, ferroelectric/piezoelectric polycrystalline bulks and thick films have been extensively studied for different applications, such as sensors, actuators, transducers and caloric devices. In the majority of these applications, the electric field is applied to the working element in order to induce an electromechanical response, which is a complex phenomenon with several origins. Among them is the field-induced movement of domain walls, which is nowadays extensively studied using piezoresponse force microscopy (PFM), a technique derived from atomic force microscopy. PFM is based on the detection of the local converse piezoelectric effect in the sample; it is one of the most frequently applied methods for the characterization of the ferroelectric domain structure due to the simplicity of the sample preparation, its non-destructive nature and its relatively high imaging resolution. In this review, we focus on the PFM analysis of ferroelectric bulk ceramics and thick films. The core of the paper is divided into four sections: (i) introduction; (ii) the preparation of the samples prior to the PFM investigation; (iii) this is followed by reviews of the domain structures in polycrystalline bulks; and (iv) thick films.