Nanopolar structures and local ferroelectricity of Sr_(0.61)Ba_(0.39)Nb_2O_6 relaxor crystal across Curie temperature by piezoresponse force microscopy

摘要

Nanopolar structures and local ferroelectricity of Sr_(0.61)Ba_(0.39)Nb_2O_6 relaxor crystal across Curie temperature have been investigated using piezoresponse force microscopy (PFM). The short-range nanopolar clusters are dominated by long-range ferroelectric order at room temperature, but exhibit themselves at higher temperature through the morphology change in written ferroelectric domains and persisting piezoresponse beyond Curie point. A maximum piezoresponse is observed at 80 ℃, which is attributed to the peak in the dielectric permittivity near the ferroelectric phase transition. Substantial asymmetry in PFM hysteresis emerges above Curie temperature, indicating an internal bias field that becomes notable in the absence of long-range ferroelectric order.