Correlation Between Microstructure and Ageing of Iron Manganite Thermistors

T. Battault , R. Legros , M. Brieu , J. Coudere , L. Bernard , A. Rousset

Negative Temperature Coefficient (NTC) thermistors made of spinel structure transition metal manganites usually display ageing phenomena under thermal stress. Their resistance drift depends on their composition, crystal structure (cubic or tetragonal) and heat treatments. We have previously shown in iron manganite thermistors, Mn3-xFexO4 (with 0 ≤x ≤1.51), that the ageing is due to the migration of Fe3+ and Mn2+ ions between tetrahedral and octahedral sites of the spinel structure. Iron manganites were investigated by Transmission Electron Microscopy (TEM) in order to relate microstructure to electrical stability. For iron manganites with iron content x ≤0.78, two dimensional defects result in a domain microstructure (microtwins). As x increases and exceeds 0.78, the domain structure gradually vanishes and transforms into a tweed microstructure (x = 1.05) and, for x > 1.30, no bidimensional defects are observed. Thus it is suggested that the microstructural disturbance plays an important role in the kinetics of the ion migration during the ageing of the studied ceramics.


Domaines: Articles anciens

T. Battault, R. Legros, M. Brieu, J. Coudere, L. Bernard, et al.. Correlation Between Microstructure and Ageing of Iron Manganite Thermistors. Journal de Physique III, 1997, 7 (5), pp.979-992. ⟨10.1051/jp3:1997169⟩. ⟨jpa-00249634⟩