Grain boundary region and local piezoelectric response of BiScO3–PbTiO3 nanoceramics prepared by combination of SPS and two-step sintering

Highly dense 0.37BiScO3–0.63PbTiO3 (BS–PT) nanoceramics with average grain sizes of 23, 33 and 70 nm were prepared by a combination of spark plasma sintering and two-step sintering methods. The microstructure, phase and piezoelectric behaviours of BS–PT nanoceramics were investigated. High-resolution transmission electron microscopy revealed that the samples had dense and thin grain boundaries. Experimental evidence demonstrated that the polarisations of the BS–PT nanoceramics were switchable and that their ferroelectricity was retained with grain sizes as fine as 23 nm. However, the local piezoelectric response showed a large fluctuation over different regions. Moreover, a significant difference between local and macro piezoelectric coefficients was observed. The properties of the grain boundary regions are the key factor to understanding the ferroelectric behaviours of BS–PT nanoceramics.