Synthesis and electrical properties of BaBiO3 and high resistivity BaTiO3–BaBiO3 ceramics

• Published in: Journal of advanced dielectrics 2016-12, Vol.6 (4), p.1650032-1-1650032-8
• Main Authors: Kumar, Nitish, Golledge, Stephen L., Cann, David P.
• Format: Article
• Language: English
• Subjects: BaBiO3; Barium titanates; BaTiO3; Bismuth; Ceramics; conduction mechanism; defects; Electrical properties; Electrical resistivity; Equilibrium conditions; Ferroelectric materials; Ferroelectricity; impedance spectroscopy; Sintering; Solid solutions; Spectrum analysis; Symmetry; synchrotron; transport properties; X-ray diffraction; X-ray photoelectron spectroscopy
• ISSN: 2010-135X; 2010-1368
• DOI: 10.1142/S2010135X16500326

Ceramics of the composition BaBiO3 (BB) were sintered in oxygen to obtain a single phase with monoclinic I 2/ m symmetry as suggested by high-resolution X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states — 3 + and 5 + . Optical spectroscopy showed presence of a direct bandgap at ∼ 2.2 eV and a possible indirect bandgap at ∼ 0.9 eV. This combined with determination of the activation energy for conduction of 0.25 eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BB. The BB ceramics were crushed, mixed with BaTiO3 (BT), and sintered to obtain BT–BB solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.