Effects of the substitution of titanium by iron and niobium on the structure and dielectric properties in BaTi1-x(Fe0.5Nb0.5)xO3 solid solution

Polycrystalline samples of BaTi1-x(Fe0.5Nb0.5)xO3 with x=0.025, 0.05, 0.075, 0.1, 0.125 and 0.15 have been synthesized by high-temperature solid-state reaction technique. The effects of cationic substitution of iron and niobium for titanium in the B sites for BaTiO3 perovskite lattice on symmetry and dielectric properties were investigated. X-ray diffraction at room temperature and dielectric permittivity in the temperature range from 85 to 500K with frequencies range from 103 to 2x105Hz, respectively, were studied. The evolution from a normal ferroelectric to a relaxor ferroelectric is emphasized. TC or Tm decreases when both iron and niobium are introduced in the lattice of BaTiO3. A high dielectric constant of around 30,000 at TC=280K was found for BaTi0.925(Fe0.5Nb0.5)0.075O3 ceramic. A relaxor ferroelectric with ΔTm=12K and ε'r about 13,800 at 10kHz with Tm=186K was found for BaTi0.875(Fe0.5Nb0.5)0.125O3 sample