Abstract
The effect of AI additions on the electrical behaviour of positive temperature coefficient of resistance (PTCR) BaTiO3 ceramic sintered in air at temperatures ranging between 1220 and 1400° C have been investigated. Two batches of material, both showing a PTCR effect, were prepared identically except that additions of AI2O3 (0.55 mol %) were made to one of them. It has been confirmed that the presence of aluminium results in an increase in the temperature at which the maximum resistivity, ϱmax, occurs as well as reducing the sintering temperature, in the presence of silicon, to 1240° C. Additionally, direct comparisons between the two materials have demonstrated that such additions result in an increase of ∼ 100% in the minimum resistivity, ϱmin, at sintering temperatures beyond 1280° C. A similar increase in ϱmax for sintering temperatures below 1360° C and a five-fold reduction in the ratio of ϱmax/ϱmin in samples sintered above 1320° C have also been attributed to the presence of aluminium. It was further found that aluminium increases the average grain size by ∼ 30% and promotes the formation of a liquid phase.
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Al-Allak, H.M., Parry, T.V., Russell, G.J. et al. Effects of aluminium on the electrical and mechanical properties of PTCR BaTiO3 ceramics as a function of the sintering temperature. J Mater Sci 23, 1083–1089 (1988). https://doi.org/10.1007/BF01154017
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DOI: https://doi.org/10.1007/BF01154017