Polar state in polycrystalline BaSn_0.3Ti_0.7O₃thin film determined from ac- & dc-field studies

The present work reports polarization response and the effects ofac- &dc-fields on 30% Sn doped BaTiO₃polycrystalline relaxor thin films as a function of temperature. Apart from the low temperature frequency dispersion in dielectric data, a frequency independent local maxima in dielectric constant and a concomitant peak in dielectric loss atT* ∼ 245 K is observed, which is unusual of bulk relaxor systems. BelowT*, dispersion in dielectric constant becomes quite evident showing signatures of non-ergodic behavior. Subsequently, the dielectric and polarization responses in ergodic (>T*) and non-ergodic (<T*) states are studied to determine the polar state in the system. Theac-field dependence of permittivity indicates the presence of domain like dynamics, predominantly in non-ergodic state. Field induced transition to ferroelectric state, both in ergodic and non-ergodic phases, is demonstrated from thedc-field studies. Further, thedc-field and polarization hysteresis studies reveal the system resembles that of anti-ferroelectric systems belowT*, a possible signature for the existence of incommensurate polar regions. These experimental results put together, provides key insights in understanding the field effects of relaxor behavior in doped barium titanate systems.