Field enhanced bulk conductivity of BaTiO3 : Mg ceramics

Abstract

The electrical conductivity of ceramics of composition Ba(Ti1−xMgx)O3−x: 0.00003 ≤ x ≤ 0.01 increases with time on application of a small dc bias voltage in the range 1 to 50 V cm−1 and at temperatures in the range 200 to 600 °C. The conductivity increase is reversible on removal of the dc bias. This low field effect is not observed in undoped BaTiO3, is intrinsic, is a property of the bulk material, is independent of atmosphere and electrode material, is not associated with charge injection into the BaTiO3 conduction band and differs from those of both varistors and memristors. The origin of the effect is attributed to a two-level electronic structure in a defect complex that contains Mg located on a Ti site, giving rise to underbonded oxide ions in the vicinity of the defect complex that are readily ionised on application of a dc bias. Conduction is predominantly p-type and therefore, holes located on oxygen, as O− ions, are more mobile than both electrons in Ti 3d levels and oxygen vacancies.