Nanoscale ferroelectric properties of PZN-PT single crystals studied by scanning force microscopy

High-resolution domain studies were performed in Pb(Zn_1/3Nb _2/3)O₃-4.5%PbTiO₃ (PZN-PT) single crystals via piezoresponse force microscopy (PFM). Irregular domain patterns with the typical sizes of 20-100 nm were observed on the (001)-oriented surfaces of unpoled samples. On the contrary, (111) crystal cuts exhibited normal micron-sized regular domains with the domain boundaries directed along allowed crystallographic planes. The existence of nanodomains in (100)-oriented crystals was tentatively attributed to the relaxor nature of PZN-PT where small polar clusters were predicted to exist upon zero-field cooling. These nanodomains were considered as the nuclei of the opposite polarization state that ease the switching process for this particular crystal cut. Local piezoelectric hysteresis was also performed by PFM on the nanometer scale. Similar switching behavior of (111)- and (100)-oriented PZN-PT crystals suggests that their superior piezoelectric properties can be related to the domain wall motion rather than to the perovskite lattice itself.