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Published online by Cambridge University Press: 22 February 2016
Phase pure Pb[(Fe0.5-xScx)Nb0.5]O3 [x= 0 to 0.5] multiferroic relaxors have been synthesized to study theeffect of Sc on dielectric phase tansition. Rietveld refinement of x-raydiffraction patterns confirm that the structure transforms from monoclinic (Cm)to rhomobohedral (R3m) at x = 0.3. Absence of low frequency dielectricresponse in compositions with low Sc content attributed to interfacialpolarizabilty arising due to differences in conductivities of grain and grainboundary. Moreover, value of diffusivity parameter (γ) of high of Sccontent compositions is near to 2, confirms relaxor charactertistic of thesecompositions. However, an essential feature of relaxors i.e., frequencydependent dielectric permittivity as a function of temperature is observed onlyin x = 0.5 composition[Pb(Sc0.5Nb0.5)O3 (PSN)]. In addition,ferroelectric phase transition temperature (Tmax) increases initiallyat lower Sc content (upto x ≤ 0.25), and further drops beyond x≥ 0.3. Such behavior of Tmax in these compositions is due to theonset of B'-B" local cation ordering at x = 0.3. Hightemperature Raman spectra of Pb(Sc0.5Nb0.5)O3(x = 0.5) confirm the stability of cation ordering in compositions withhigh Sc content well above the phase transition temperature.