Ferroelectric properties and polarization dynamics in Ba4Sm2Ti4Ta6O30 tungsten bronze ceramics

Ferroelectricity and polarization reversal dynamics in Ba4Sm2Ti4Ta6O30 tungsten bronze ceramics were investigated by measuring dielectric spectra and the evolution of hysteresis loops over a wide temperature range. With decreasing temperature, the dielectric properties and differential scanning calorimetry results showed diffuse peaks at similar to 280K with large thermal hysteresis, suggesting a first order ferroelectric transition. A dielectric relaxation was observed at low temperature that followed the Vogel-Fulcher relationship. The saturation and remanent polarizations of the Ba4Sm2Ti4Ta6O30 ceramics showed remarkable dependence on the applied field and temperature. The temperature dependence of the coercive field was divided into three linear regions and fitted to the Vopsaroiu model. Activation energies for polarization reversal of 0.73, 0.79, and 0.65 eV were determined for the following three regions: (I) the diffuse ferroelectric transition region (323.15-293.15K), (II) the region just below the ferroelectric transition temperature (293.15-233.15 K), and (III) the low temperature relaxation region (233.15-173.15K), respectively. The decrease of the activation energy in region III was attributed to the low temperature relaxation of Ba4Sm2Ti4Ta6O30. (C) 2016 AIP Publishing LLC.