δ-Bi2O3 thin films deposited on dense YSZ substrates by CVD method under atmospheric pressure for intermediate temperature SOFC applications

Thin films of δ-Bi2O3 were grown on a dense Yttria Stabilized Zirconia (YSZ) substrate under atmospheric pressure by means of halide chemical vapour deposition (AP-HCVD) using BiI3 and O2 as starting materials. X-ray diffraction (XRD) profiles confirm that above 700 °C δ-Bi2O3 film with a cubic structure is formed. When the δ-Bi2O3 is deposited at 850 °C, the 〈111〉 direction is preferred. Scanning electron microscopy (SEM) observation revealed that the surface of the film appeared granular and homogeneous with average grain size about 15 μm. The thermal stability investigation shows that the δ-Bi2O3 films keep its fcc structure up to an annealing temperature of 350 °C, above which it transforms into the γ-Bi2O3 bcc structure.