Structural, dielectric and magnetic properties of Cd/Pb doped W-type hexaferrites

• W type Ba(Zn0.5Cd0.5)2Fe16O27 and Ba(Zn0.5Pb0.5)2Fe16O27 hexaferrites were prepared.
• BZPFO has more resistivity and low values of σa.c., ε′ and tan δ than BZCFO.
• BZCFO has higher saturation magnetization and lower coercivity than BZPFO.

W-type hexaferrites having compositions Ba(Zn0.5Cd0.5)2Fe16O27 (BZCFO) and Ba(Zn0.5Pb0.5)2Fe16O27 (BZPFO) were synthesized by solid state reaction method at high annealing temperature. Their dielectric and magnetic properties as a function of temperature and frequency have been studied. X-ray analysis confirms the presence of W-type hexaferrite phase structure. SEM analysis presented heterogeneous hexagonal shape and sizes of grains. Analysis of Nyquist plots of prepared samples revealed the contribution of electrically active regions corresponding to grains and grain boundaries. The reciprocal temperature dependence of dc electrical resistivity (ρ) satisfies the Arrhenius relation which depicted the semi-conducting behavior of the samples. The variation of dielectric constant (ε′) and dielectric loss (tan δ) with temperature (323 K–573 K) and frequency (1 kHz–5 MHz) are studied. Analysis of the experimental conductivity data and ‘s’ parameter shows that correlated barrier hopping (CBH) mechanism is the most probable mechanism of conduction for BZCFO sample; whereas for BZPFO hexaferrite, both correlated barrier hopping (CBH) and quantum mechanical tunneling (QMT) model are applicable for conduction. The BZCFO sample has higher value of saturation magnetization and lower coercivity than BZPFO sample due to the preference of Cd2+ for tetrahedral sites and decrease in number of spin-down magnetic ions.