Effects of Sm substitution on ferroelectric domains and conductivity in bismuth ferrite ceramics

The large piezoelectric coefficient and multiferroicity of bismuth ferrite (BFO) make it an attractive candidate for lead-free ferroelectric devices. However, large leakage currents have limited broader applications. Rare-earth substitutions in BFO have been shown to improve ferroelectric and magnetic properties. In this work, we employed piezoresponse and conductive atomic force microscopy to study ferroelectric domains in Bi_1-xSm_xFeO₃ (x = 0-0.150) grown by the co-precipitation method. The combined piezoresponse and conductivity measurements can directly visualize the local ferroelectric domains under different sample bias. At Sm mol% > 7.5, Sm-substitution effectively lowers defect-generated conductivity. At Sm mol% < 7.5, conductivity increases due to conductive domain walls inside sample grains. The surfaces of these conductive samples exhibit a p-type rectifying behavior while the bulk is n-type. Our work details how the local piezoelectric properties and transport behaviors of BFO ceramics change as a function of Sm-substitution.