Relaxor ferroelectric behavior:An approach considering both the dipolar and electrical conductivity contributions

The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approximation to the dynamical behavior of the PNRs has been discussed using Cole-Cole’s relaxation model and Jonscher’s Universal Relaxation Law.The analysis considers both the dipolar contribution and those ones associated with DC and AC electric conductivities,this latter not being previously reported in the literature for relaxor materials.The effectiveness of the developed model has been verified from the agreement between the experimental data and the theoretical calculations.This study also offers an indirect method to predict the DC component of the electrical conductivity.

Energy storage and relaxor behavior in(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]O_(3)ferroelectric ceramic

(Pb_(0.8)Ba_(0.2))[(Zn_(1/3)Nb_(2/3))_(0.7)Ti_(0.3)]O_(3)relaxor-type ferroelectric ceramics was obtained via classical solid-state reaction.The hysteresis loop results were discussed in the frame of ergodicity criterium around the characteristic ferroelectric relaxor freezing temperature.Slimer hysteresis loops were observed below the freezing temperature reflecting an ergodic relaxor behavior.Above this temperature,estimated around 223K for the studied system,larger and unsaturated like ferroelectric hysteresis loops were observed.This temperature also coincides with the slope change on maximum polarization and inflection point of remnant polarization curves.Energy storage,energy loss and efficiency values were determined in a wide temperature range.While the recoverable energy density shows relatively low values(0.23 J/cm^(3)),there are interesting behaviors for this parameter and for the efficiency,since the two physical quantities increase versus temperature and the efficiency even reaches the value of 97%.

Structural,microstructural and dielectric characterizations of(Bi_(0.5)Na_(0.5))TiO_(3) based lead-free ferroelectric ceramics

(1-x)(Bi_(0.5)Na_(0.5))TiO_(3)-xBaTiO_(3) lead-free ceramics have been obtained from the conventional solid-state reaction sintering method.The structural properties were investigated from X-ray diffraction and Raman spectroscopy techniques.Results revealed well-crystallized ceramic samples with perovskite structure.Microstructural properties,obtained from scanning electron microscopy measurements,have shown high density with very low porosity level.The dielectric response,analyzed as a function of the temperature and several frequencies,showed very broad peaks with a strong frequency dependence of the temperature for the maximum dielectric permittivity for the modified system.Results were analyzed considering the influence of the BaTiO3 content on the studied physical properties.