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Impedance Spectroscopy Study of Niobium‐Doped Strontium Titanate Ceramics
Author(s) -
Abrantes Joao C. C.,
Feighery Alan,
Ferreira António A. L.,
Labrincha Joao Antonio,
Frade Jorge R.
Publication year - 2002
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.1151-2916.2002.tb00523.x
Subject(s) - strontium titanate , niobium , materials science , dielectric spectroscopy , analytical chemistry (journal) , capacitance , atmospheric temperature range , activation energy , condensed matter physics , dielectric , microstructure , spectroscopy , ceramic , mineralogy , chemistry , thermodynamics , physics , composite material , metallurgy , optoelectronics , electrode , chromatography , quantum mechanics , electrochemistry
Impedance spectroscopy was used to study the temperature dependence of the resistance and capacitance of niobium‐doped strontium titanate ceramics and also to identify the main contributions determining potential applications. Nyquist plots ( Z ″ versus Z ′) show a main contribution in the intermediate‐frequency range, with a peak at ∼1 kHz at 500°C. The activation energy of this resistance contribution is close to 1.5 eV. Modulus representations (log M ″ versus log f ) show a second contribution in the high‐frequency range, with a peak at ∼100 kHz at 500°C. This resistance contribution is much smaller, and its activation energy is also lower (close to 0.8 eV). The capacitance of the intermediate‐frequency term increases from ∼0.1 μF/m at 700°C to ∼1 μF/m at 425°C. The capacitance values of the high‐frequency contribution are also >0.1 μF/m, much higher than expected for the bulk. These contributions might be related to differences between the intergrain interfaces and outer grain shells, as suggested by SEM microstructures with core–shell formations. Representations of 1/ C against temperature suggest a Curie–Weiss law for the main contribution in the intermediate‐frequency range, with a T C of ∼400°C. However, the temperature dependence of the overall dielectric constant measurements (at constant frequency) fail to show a clear maximum, probably due to an additional low‐frequency contribution ascribed to the Pt/SrTi 1− x Nb x O 3−δ interface.