The dielectric properties (dielectric constant and loss) for the system Cu_xFe_3−xO₄ with x = 1.0, 0.8, 0.6, 0.4 and 0.2, were studied in the temperature range 300 ∼ 800 K and also in the frequency range 1 kHz ∼ 1 MHz. A.c. conductivity was derived from dielectric constant and loss tangent data. The conduction in this system is interpreted as due to small polaron hopping. The dielectric relaxation was observed for the compositions with tetragonal structure whereas normal behaviour was observed for cubic structure.

Polycrystalline Pb(Mn_0.5W_0.5)O₃, a ferroelectric oxide having perovskite structure, was prepared by high temperature solid state reaction technique. Preliminary X-ray diffraction analysis confirms single phase formation with the lattice parameters 𝑎 = 7.2501 Å, 𝑏 = 8.1276 Å and 𝑐 = 12.0232 Å. Room temperature dielectric constant (𝜀' ) and loss tangent (tan 𝛿) were scanned with respect to frequency in the range 100 Hz–1 MHz. Detailed study of dielectric constant and electrical conductivity reveals a phase change around 400 K, which is quite different from those in the other materials of the same type. Further, the seebeck coefficient (𝛼) is temperature independent. The conduction is interpreted as due to small polaron hopping.