Figure 4 shows the polarization-fie

Figure 4 shows the polarization-field (P-E) hysteresis loop of the BT-75nm. A hysteresis loop indicates the ferroelectric switching with a remanent polarization, Pr, of 15.0 µC cm-2 and coercive, EC, of 18.6 kV cm-1. There are very few reports for the “macroscopic”ferroelectric switching behavior in the BaTiO3 nanocrystalline ceramics[37,38,49,50]. The bulk P-E hysteresis were often the nearly linear so that evidence of the ferroelectric switching in the nano-grain ceramics has been limited in the “local” phenomena by the piezoresponse force microscopy.[49,50] The reason why the BT-75nm in the present work can still show macroscopic ferroelectric switching behavior is not clear. It could be owing to sharp grain boundary microstructures that minimize the dilution of ferroelectric properties resulting from the non-ferroelectric grain boundary layers, or simply due to relatively larger grains compared to 20-50 nm in the ref [38,49,50]. In contrast to the previously thought, recent studies indicate the nanostructure could enhance the ferroelectric properties[51,52]. The understanding of the structure-property relationship in the BaTiO3 nanocrystalline ceramics is under further investigation and is beyond the scope of this report.