High Thermoelectric Performance Of Unsintered NaCo2O4 Nanocrystal
Mehmet OkanErdal, Mustafa Koyuncu, İbrahim Uslu
Index Terms: Thermoelectric properties, Sodium Cobal OxideNanocrystalline, Electrospinning
Abstract: Sodium cobaltite (NaCo2O4) nano crystalline thermoelectric materials were obtained using electrospinning technique. Electrospunnanofibers was calcined at 800 oC and sintered at 850 oC in open air atmopshere. We have investigated the microstructure and thermoelectric properties of the sintered and unsintered samples for analysis sintering effect. The calcined sodium cobaltite crystal structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Products molded by cold pressing method, and one of the pellets were sintered at 850 oC by conventional sintering, the other not subjected to the sintering process. Thermoelectric properties of the both materials were measured by PPMS system in the temperature range 10-300 K. The dimensionless figure of merit (ZT) values at 300 K is 4×〖10〗^(-5)and 9×〖10〗^(-5) for sintered and unsintered samples respectively. Although conventional sintered technique increase thermoelectric power and thermal conductivity approximately % 50 but it 4-fold decreased electrical conductivity.
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