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Resistance Degradation of Iron‐Doped Strontium Titanate Investigated by Spatially Resolved Conductivity Measurements
Author(s) -
Rodewald Stefan,
Fleig Jürgen,
Maier Joachim
Publication year - 2000
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2000.tb01499.x
Subject(s) - materials science , conductivity , strontium titanate , grain boundary , dielectric spectroscopy , ionic conductivity , vacancy defect , doping , analytical chemistry (journal) , thermal conduction , mineralogy , spreading resistance profiling , chemical physics , condensed matter physics , composite material , chemistry , thin film , microstructure , electrode , nanotechnology , electrolyte , optoelectronics , electrochemistry , chromatography , physics
Resistance degradation in perovskites generally is assumed to be caused by stoichiometry variations that occur during high field stress. According to this assumption, distinct conductivity profiles should develop during degradation. In this study, microcontact impedance spectroscopy is used to determine the conductivity profiles in iron‐doped strontium titanate after dc stress with a spatial resolution of ∼20 μm. All the features of the characteristic conductivity distributions experimentally observed in single crystals agree with the theoretically predicted distributions and confirm the validity of the stoichiometry polarization model. The degraded samples are concluded to exhibit an oxygen‐vacancy enhancement at the cathode and a vacancy depletion at the anode, which leads to a hole–ionic–electron conduction ( p – v – n ) transition of the conduction mechanism. Conductivity measurements at polycrystals revealed “subprofiles” within single grains, which can be explained by the blocking character of grain boundaries and the resulting accumulation of vacancies on one side of the grain boundaries and a depletion of vacancies on the other side.