ABSTRACTPhase pure Pb[(Fe0.5-xScx)Nb0.5]O3 [x
= 0 to 0.5] multiferroic relaxors have been synthesized to study the
effect of Sc on dielectric phase tansition. Rietveld refinement of x-ray
diffraction patterns confirm that the structure transforms from monoclinic (Cm)
to rhomobohedral (R3m) at x = 0.3. Absence of low frequency dielectric
response in compositions with low Sc content attributed to interfacial
polarizabilty arising due to differences in conductivities of grain and grain
boundary. Moreover, value of diffusivity parameter (γ) of high of Sc
content compositions is near to 2, confirms relaxor charactertistic of these
compositions. However, an essential feature of relaxors i.e., frequency
dependent dielectric permittivity as a function of temperature is observed only
in x = 0.5 composition
[Pb(Sc0.5Nb0.5)O3 (PSN)]. In addition,
ferroelectric phase transition temperature (Tmax) increases initially
at lower Sc content (upto x ≤ 0.25), and further drops beyond x
≥ 0.3. Such behavior of Tmax in these compositions is due to the
onset of B'-B" local cation ordering at x = 0.3. High
temperature Raman spectra of Pb(Sc0.5Nb0.5)O3
(x = 0.5) confirm the stability of cation ordering in compositions with
high Sc content well above the phase transition temperature.
Study of physical properties of a ferrimagnetic spinel Cu1.5Mn1.5O4: spin dynamics, magnetocaloric effect and critical behavior
