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Microcontact Impedance Spectroscopy at Single Grain Boundaries in Fe‐Doped SrTiO 3 Polycrystals
Author(s) -
Rodewald Stefan,
Fleig Jürgen,
Maier Joachim
Publication year - 2001
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.1151-2916.2001.tb00693.x
Subject(s) - grain boundary , materials science , dielectric spectroscopy , condensed matter physics , crystallite , depletion region , electrical impedance , schottky barrier , composite material , grain boundary diffusion coefficient , mineralogy , layer (electronics) , metallurgy , microstructure , optoelectronics , chemistry , electrical engineering , electrode , physics , diode , electrochemistry , engineering
Microcontacts on adjacent grains of polycrystalline Fe‐doped SrTiO 3 samples have been used to locally investigate the properties of individual grain boundaries. Impedance spectroscopy was employed to separate bulk and grain boundary impedances. Experiments at about 30 different grain boundaries permit far‐reaching conclusions on the distribution of grain boundary resistances, capacitances, and peak frequencies measured between adjacent grains. The rather narrow distribution of the grain boundary peak frequencies indicates a narrow distribution of grain boundary resistivities. All features (e.g., nonlinear current–voltage characteristics, grain boundary thickness, temperature dependence) are in accordance with the assumption of space charge depletion layers (double Schottky barriers) as the origin of the enhanced grain boundary resistivity. The average barrier height measured was about 630 mV. For comparison conventional (macroscopic) impedance measurements on a polycrystal were also performed and a brick layer model was used to extract effective properties. The reasonable agreement between these effective parameters and the average of the locally obtained parameters demonstrates that, in this case, a brick layer analysis of conventional impedance experiments yields satisfying estimates of the grain boundary properties.