Diffuse phase transition in BaTi1-xSnxO3 ceramics:: An intermediate state between ferroelectric and relaxor behavior

Dielectric relaxation and polar structures of BaTi1-xSnxO3 ceramics, x=0.10-0.20, are investigated by means of dielectric spectroscopy and piezoresponse force microscopy. A transition regime between normal ferroelectric and relaxor behaviors is encountered. In the compositions with x=0.10, a complex domain pattern confirming the ferroelectric state is observed. Strong dielectric relaxation around T-m is attributed to domain wall motion. On the other hand, the dielectric spectra in the sample with x=0.20 are very similar to those observed in relaxor ferroelectrics. Analysis of the relaxation spectra at the intermediate concentration, x=0.15, reveals both domain wall response and an additional contribution related to mesoscale polar structures. The appearance of relaxor behavior in BaTi1-xSnxO3 is discussed within the framework of the random field model.