AFe 1/2 B 1/2 O3(A-Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were synthesized and temperature dependencies of the dielectric permittivity were measured at different frequencies. The experimental data obtained show very high values of the dielectric permittivity in a wide temperature interval that is inherent to so-called high-k materials. The analyses of these data establish a Maxwell-Wagner mechanism as a main source for the phenomenon observed.

In the present study, we diluted either A- or B- sublattice of perovskite multiferroic PbFe(0.5)Nb(0.5)O(3) (PFN) and studied the changes of the magnetic and ferroelectric phase transition temperatures and dielectric properties caused by such dilution. Dielectric studies of PFN single crystals show that, in contrast to the commonly adopted view, the ferroelectric phase transition in PFN is non-diffused and the relaxor-like behavior usually observed in ceramic samples has an extrinsic nature. A-site substitutions (Ba, Ca) lead to the smearing of the permittivity-temperature maximum, lowering its maximum temperature, T(m) and inducing relaxor behavior. B-site diluting of PFN by Ti increases T(m) and only slightly affects the permittivity maximum diffuseness. Both A-site and B-site substitutions in PFN lead to lowering of its Neel temperature, T(N). However, above a certain compositional threshold, fast lowering of T(N) stops and a new magnetic state with comparatively high (~50K) transition temperature becomes stable in a rather wide compositional range.

No abstract

No abstract

No abstract