High dielectric constant and low optical band gap studies of La-modified Ba(Fe0.5Nb0.5)O3 ceramics

Ba1-xLa2x/3(FeNb)0.5O3/BLFN (x = 0, 0.02, 0.04, 0.06, 0.08) ceramics in single perovskite phase were synthesized by solid state reaction route. Dielectric constant (εr) increased with the increase of La content in the BLFN ceramic samples. Defects and the charge compensation mechanisms were used to account the observed high εr and the relaxor like behavior of the BLFN ceramic samples. All the BLFN ceramic samples exhibited the wider absorption bands (200-900 nm) and the narrow optical band gaps (∼1.3 eV). Dielectric relaxation and the narrow band gaps suggested the formation of oxygen vacancies in the BLFN ceramic samples.