Dielecric relaxation and conduction mechanism of dysprosium doped barium bismuth titanate Aurivillius ceramics

In this report, we present the structure, electrical properties and optical study of dysprosium doped bismuth layer-structured BaBi₄Ti₄O₁₅ (BBT) with a general formula Ba(Bi_1−xDy_x)₄Ti₄O₁₅ (BDBT), prepared by solid state reaction route. The X-ray diffraction study shows a single phase orthorhombic structure with a space group A2₁ am in all compositions. The relaxation and conduction mechanism was studied by frequency and temperature dependent impedance spectroscopy. Impedance studies show a non-Debye type relaxation, and relaxation frequency shift to the higher side with an increase in temperature indicating conduction in material and favouring the long range motion of mobile charge carriers. The Nyquist plot shows overlapping semicircles, for grain and grain boundary of Dy doped BBT ceramics. The Kohlrausch–Williams–Watts function is used to explain the modulus analysis and confirms the coexistence of grain and grain boundary effects. The frequency dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated and the spectra follow the universal power law. The variation of DC conductivity confirms that the BDBT ceramics exhibit negative temperature coefficient of resistance behaviour in high temperature. Activation energies are obtained from the Arrhenius fitting of impedance and conductivity plots.