Metal oxide semiconductor has attracted so much attention due to its high carrier mobility. Herein, thermoelectric study of nanocrystalline SnO2 through a simple co-precipitation method is conducted to enhance the Seebeck coefficient (S). X-ray diffraction, thermogravimetric analysis (TGA), resistivity (r), Seebeck coefficient (S), and power factor (PF) measurements are conducted to analyze the thermoelectric properties of the material. The measurements show that there are two interesting results, which are the unusual resistivity behavior and the high value of the S. Resistivity behavior shows a non-reflective intermediate semiconductor-metals behavior where the turning point occurs at 250 o C. This behavior is strongly correlated to the surface oxide reaction due to annealing temperature. The maximum S likely occurs at 250 ºC, since the curve shows a slight thermopower peak at 250 ºC. The value of the S is quite high with around twenty times higher than other publications about SnO2 thermoelectric material, this happens due to the bandgap broadening. The energy gap of SnO2 calculated using density functional theory (DFT), which was performed by Quantum Espresso 6.6. The result shows that there is a broadening energy gap at different momentum or wave factor. Nanocrystalline semiconductors material is giving an impact to increase the width of bandgap due to quantum confinement and could enhance the thermopower especially in SnO2 nanocrystalline
Among magnetic materials, ferrites have significant attention due to their potential application, such as magnetic recording, sensors, radar-absorbent materials, catalysts, and energy-storage devices. One of the ferrites family, FeMnO3, has been synthesized by solid-state reaction using Fe2O3 powder with an excess of 0.02% MnO2 powder in the stoichiometric composition. The structural and morphological properties have been performed using XRD and SEM at room temperature. The diffraction peaks in the pattern were indexed as FeMnO3 with a cubic (bixbite, Ia3) crystal structure. It showed no additional peaks due to impurities. The SEM image reveals the grains nucleate in a cube-like shape. Some of the particles also seem to agglomerate into larger particles. The magnetic characterization was carried out using VSM at room temperature. The magnetic hysteresis loop (M-H curves) notices the ferrimagnetic behavior. The results show remnant magnetization (Mr), coercive field (Hc), magnetic moment (µB), and anisotropy constant of FeMnO3 are 0.296 emu/g, 299 Oe, 0.046 emu/mol, and 0.1 when the external field is 70˚-80˚ from the easy axis, respectively.
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