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.
Highlights
Calcium aluminate compounds consist of a wide range of combinations of calcium oxide and aluminum oxide, and many of these materials are found in cement technology as hydraulic materials.[1]
The identification of the phases of the investigated calcium aluminate powders at a temperature of 1350 oC and pellets calcined at 1350 oC was carried out by X-ray diffraction (XRD) before treatment in an air-controlled atmosphere using a Philips model X’Pert MPD diffractometer
Optical measurements using ultraviolet (UV)-visible spectroscopy were in investigated calcium aluminate powders at a temperature of 1350 oC, with a Varian Cary 5000 device having a wavelength range of 200 to 800 nm
Summary
Calcium aluminate compounds consist of a wide range of combinations of calcium oxide and aluminum oxide, and many of these materials are found in cement technology as hydraulic materials.[1] This system is attractive as ceramic materials for high-temperature refractory applications.[2] These compounds play important roles in the steel industry as metallurgical slag.1) Calcium aluminates have a wide range of potential technological applications due to their unusual optical, electrical, thermal, and mechanical properties.[3] The calcium aluminate phase diagram shows a low melting point, the eutectic point, located at 1400 and 1395 oC, where C12A7 (mayenite), and C3A (celite) are the main coexisting phases They have similar cubic structures, and some studies[4] reported that the best sintering temperature to attain that biphasic material is about 1350 oC. To deduce the calcium aluminate defect chemistry in this SMCM biphasic composition, the electrical transport mechanism was investigated and discussed
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