Effect of sintering atmosphere on the electrical properties of lanthanum doped barium titanate: an impedance spectroscopic study

The electrical properties of 0.1 mol% La-doped BaTiO₃ was investigated by impedance spectroscopy after sintering the sample in air and H₂ at 1350 °C. H₂-sintered sample showed more semiconducting nature than air-sintered one due to a higher level of oxygen loss accompanied by reduction of Ti⁴⁺ to Ti³⁺. The overall resistance of the sample decreased with rise in temperature and change of sintering atmosphere from oxidizing to reducing. The higher value of activation energy obtained from Arrhenius activated hopping frequency f _H for H_2-sintered sample describes the delayed onset of frequency-dispersion in the conductivity curves than the air-sintered sample. The conductivity relaxation was studied in the light of frequency-dependence of the imaginary part of electric modulus and scaling studies of the real and imaginary parts of Z* elucidating the thermally activated relaxation dynamics. (paper)