Enhanced dielectric property of Ni ferrite by Sm and Ho substitution

The enhancement in the dielectric constant of NiO Fe1.925 Sm0.075 O3 and NiO Fe1.925 Ho0.075 O3 when compared to pure NiO Fe2 O3 is reported. Sm- and Ho-substituted Ni ferrites crystallize in the cubic inverse spinel phase. Frequency variation in the dielectric constant shows the dispersion that can be modeled with a modified Debye's function, which considers the possibility of more than one ion, contributing to the relaxation. Temperature-dependent electrical conductivity curves exhibit two distinct regions indicative of two different types of conduction mechanisms, the small polaron and variable range hopping, at 220-300 and 160-220 K regions, respectively. © 2010 The Electrochemical Society.