Preparation and Characterization of Ca3Co4O9 Thin Films on Polycrystalline Al2O3 Substrates by Chemical Solution Deposition

Ca3Co4O9 thin films have been first prepared on polycrystalline Al2O3 substrates using chemical solution deposition method by multiple annealing processing. It is observed that the derived thin films are c-axis oriented although the substrates are polycrystalline Al2O3 substrates, suggesting the self-assembled c-axis orientation. The annealing temperature effects on the properties are investigated and discussed. The best performances are attributed to the 850 °C-annealed sample, whose resistivity, Seebeck coefficient and power factor at 300 K are 7.4 mΩ cm, 117 μV/K and 0.18 mW/m K−2 respectively, which is even better than those of the thin films deposited on single crystal substrates. The results will provide an effective route to optimize the properties of Ca3Co4O9 thin films using chemical solution deposition by multiple annealing processing even the substrates are polycrystalline.