PREDICTION OF DIELECTRIC DISPERSION FOR LEAD BASED PEROVSKITES AND STUDY OF LOCAL DIELECTRIC RESPONSE IN 0.75Pb(Mg1/3Nb2/3)O3–0.25PbTiO3

Relaxor ferroelectrics have been used in a variety of applications, such as piezoelectrics, capacitors, and transducers. Relaxors exhibit broadened permittivity peaks with dispersion of the frequencydependent dielectric constant. In particular, T ;max, the temperature maximum of the ð!Þ, follows the Vogel Fulcher relationship described by ! 1⁄4 !0e Ua=kBðT ;max Tf Þ; ð1Þ where ! is a frequency of applied ̄eld, !0 is an attempt frequency, Tf is the freezing temperature at which the relaxation frequency vanishes, kB is the Boltzmann constant, and Ua is the Vogel Fulcher activation barrier. Following the work of Burns and Dacol, the unusual dielectric and structural properties of relaxors have been ascribed to the appearance of polar nanoregions (PNR) inside the nonpolar matrix at the Burns temperature Tb above the Curie temperature Tc. For some years, the PNR were thought to be formed due to the presence of nanoscale compositional inhomogeneities. Such inhomogeneities would lead to strong random electric ̄elds and a smearing out of the ferroelectric jjCorresponding author. Journal of Advanced Dielectrics Vol. 2, No. 2 (2012) 1241009 (6 pages) © World Scienti ̄c Publishing Company DOI: 10.1142/S2010135X12410093