High-Temperature Electrical Transport Property of Misfit Cobaltite of Ca3-xNdxCo4-xCuxO9 (x = 0.0 – 0.4)

Abstract

Polycrystalline samples of the Ca3-xNdxCo4-xCuxO9 (x = 0.0 - 0.4) were prepared by the sol-gel cum combustion method using sucrose to investigate the effects of the coupled substitution of Nd and Cu on Ca and Co sites simultaneously on electrical property of Ca3Co4O9 (Co349). The products were characterized by powder x-ray diffraction (XRD), thermogravimetry (TG) / differential thermal analysis (DTA) and scanning electron microscopy (SEM). Powder XRD patterns reveal the formation of single-phase products up to x = 0.4. Coupled substitution increases the solubility of Cu on Co site, in contrast to the limited solubility of Cu (x = 0.3) when separately substituted. TGA confirms the formation of the Ca3Co4O9 phase at around 680 0C. The grain size of the parent and substituted products is in the range of 200-250 nm. Electrical resistivity (ρ) measurement was performed in the temperature range of 300 - 800 K. Electrical resistivity (ρ) of parent sample shows metallic type conduction behavior up to 500 K and above 500 K, it shows semiconducting behavior. All the substituted compositions show semiconducting behavior with increasing electrical resistivity with increasing x. The conduction mechanism was also analyzed. Parent and substituted samples behave thermally activated conduction mechanism in the temperature range of 600 – 800 K.