Conductivity Injection and Extraction in Polycrystalline Barium Titanate

Abstract

Direct current electric fields applied to polycrystalline barium titanate cause slow changes with time of current, potential distribution, and coloration. At temperatures between 250° to 300°C and with several thousa.nd volts/em applied, the current increases initially, then decreases, and then increases again. An analysIs of the potential distribution indicates injection of a high conductivity region from the cathode whereby the fi~l? at th~ cathode is decreased and the field at the anode is increased, followed by injection of a low conductivity regIOn from the anode which travels to the cathode, causing a high field at the cathode and renewed injection of high conductivity from the cathode. Drift mobilities for the low conductivity region have been estimated.

Electrical Properties of Acceptor Doped BaTiO3

“…However, the specimen equally co-doped with 0.5 mol% Mg and Mn showed higher leakage currents and failure occurred earlier than the un-doped BaTiO 3 . The high leakage current with short lifetime of 0.5 mol% Mg-doped BaTiO 3 is due to the electro-migration of oxygen vacancy from anode to cathode under the continuous dc field [12][13][14][15]. This result demonstrates that leakage currents of acceptor doped BaTiO 3 under dc field are effectively suppressed by Mn doping as long as the Mn doping level is greater than Mg contents.…”

“…The increase in oxygen vacancy suppresses the reduction of BaTiO 3 specimens and moves the n-type range to lower Po 2 , resulting in the highly insulating p-type material. However, the oxygen vacancy is the most mobile species in BaTiO 3 lattices and the electromigration of charged oxygen vacancies in dc field is accountable for the electrical degradation of BaTiO 3 -based ceramic capacitors [12][13][14][15].…”

Electrocoloration and oxygen vacancy mobility of BaTiO3

“…17 21 and 625 nm. 11 As regards the origin of these two colors, the authors attributed the anodic brown color to V centers 10 and the cathodic blue color to F centers, 10 small polaron absoption, 19 impurity level to conduction band transition, 20 or Ti-ion polarization. 18 Quite recently, Schrader et al 17 have concluded that the optical absorption in the NIR, which is responsible for the blue color of strongly reduced BaTiO 3 , is due to small polaron hopping of electrons of Ti 3+ -Ti 4+ charge transfer type.…”

“…2,[7][8][9] For the system of BaTiO 3 , there have been reports on the electrocoloration, [9][10][11][12][13][14][15] but the authors' main concern was mostly on the origins of color or the correlation of color change to the IR degradation ͑or conductivity change͒ rather than on the mobility itself, thus only a few scattered data on oxygen vacancy mobility are available. 5,6,9,10,13,15 As regards the electrocoloration of BaTiO 3 , it seems to have been generally agreed upon that a brown color emanates from the anode and a blue color from the cathode, 10,11,13 even though there are differences in shade depending on the authors and depending on observation temperatures. The nature of their origins, however, still remains unelucidated.…”

Influence of Dislocations in Transition Metal Oxides on Selected Physical and Chemical Properties

“…Another way to switch dislocations in both materials from being semiconducting (corresponding with their original state in the stoichiometric crystal) to become metallic filaments is possible using electrical polarization with appropriate voltage and current. Although it was already presented in 1962 that under external electrical stimuli the resistance of polycrystalline BaTiO3 can be reduced [254], only as recently as 1992 it was observed for KNbO3 that the resistance of single crystals can be easily increased by many orders of magnitude up to metallic behavior by the application of a constant voltage or constant current polarization [59]. As an effect, a dense set of filaments are being created between the position of the geometrical position of the cathode and a progressing virtual cathode.…”