Mixed electrical conduction of calcium aluminates synthesized by polymeric precursors

Abstract

A study of the electrical transport properties of calcium aluminate (CA) with coexisting C3A and C12A7 phases was carried out. In this work, powders resulting from synthesis based on the polymer precursor method. The resulting product was characterized by means of XRD, Raman, and UV-visible analysis to obtain the optical BG and by EIS. From the XRD and Raman analyses, the presence and coexistence of the two self-modified phases were confirmed. In this biphasic composition, celite phase was estimated to be the major phase. An optical BG of 5.69 eV at room temperature was calculated, and under the condition of a reducing atmosphere in the temperature range of 750-950 ºC, an activation energy for conduction of 2.98 eV was determined by EIS measurements. Further, in this biphasic sample, the electronic conduction transport might be governed by the mayenite minor phase due to its large defect nature and concentration compared to celite. In oxidizing conditions, the activation energy for electrical conduction was 1.42 eV, which is somewhat higher than that observed by other authors in mayenite single phase; this result was explained by taking into account the coexistence of biphasic material and an actual chemical defect scenario in SMCM is discussed.