Mr. Or Zabari - MSc candidate
David Wang Auditorium, 3rd floor Dalia Meidan Bldg.
Calcium manganite (CaMnO3)-based oxides are applied for thermoelectric (TE) energy conversion, and are inexpensive, nontoxic and possess chemical and thermal stability. The major challenge in their application is their relatively low electrical conductivity; the latter can be enhanced by doping, thereby affecting their transport mechanisms.
We investigate Ca1-xYxMnO3 compounds with x= 0.03 and 0.13. We prepare the materials applying solid-state reaction (SSR) procedures including ball-milling (BM) of the powders to increase the relative density of the sintered samples. We characterize the materials applying x-ray diffraction (XRD) and scanning electron microscopy (SEM). The sintered compounds exhibit relative density values as high as ca. 95% upon BM rate > 200 RPM. Consequently, the electrical conductivity increases by ca. 2.4 times at room temperature for Ca0.97Y0.03MnO3 due to BM at 250 RPM, compared to the manually milled sample. We obtain a maximum TE power factor (PF) value of 3362 10¬-7∙W/m∙K2 for Ca0.97Y0.03MnO3 at 650 K due to BM at 250 RPM. We, finally, analyze the electrical transport coefficients in terms of the small polaron hopping model. The calculated polaron hopping energy exhibits a minimum value for intermediate BM rates, yielding maximum PF-values. We conclude that electronic transport properties of Y-doped CaMnO3 can be tuned by controlling the BM conditions. This study can serve as a guideline for doping and processing of similar materials for TE energy conversion at elevated temperatures.
B.Sc. in Material Science and Engineering with Chemistry from the Technion.