Shufang Wang,Shanshan Chen,Guoying Yan,Fuqiang Liu,Shouyu Dai,Jianglong Wang,Wei Yu,Guangsheng Fu
c-axis oriented nanocrystalline Bi 2 Sr 2 Co 2 O y thin films with the average grain size of 25 nm have been achieved by chemical solution deposition combined with a rapid annealing process in oxygen. The resistivity and Seebeck coefficient of the nanostructured films are about 7.0 mΩ·cm and 171 μV/K at 873 K, resulting in a power factor 2–3 times larger than that of the best reported value in the coarse-grained Bi 2 Sr 2 Co 2 O y polycrystalline bulks. Since the thermal conductivity can be greatly reduced due to the increased phonon scattering at the grain boundaries of nanocrystalline films as well as at film surface and at film/substrate interface, great improvements in the ZT are expected in the nanocrystalline Bi 2 Sr 2 Co 2 O y thin films .
The Aurivillius compound Pb x Bi 6− x Fe 0.5 Co 0.5 Ti 4 O 18 thin films were prepared via chemical solution deposition method and the influence of Pb 2+ ions doping on the structure, ferroelectric and leakage properties were studied. With the increasing concentration of Pb 2+ ions, the lattice distortion is increased and the growth of the films along ab plane is promoted. The calculation results show that the internal stress of the films increases with the increase of Pb 2+ concentration. For the samples with low Pb 2+ doping concentration ( x < 0.6), the leakage current densities are also decreased, which can be attributed to the decrease in oxygen vacancy concentration. Due to the enhanced lattice distortion and decreased leakage current densities, the ferroelectric properties are improved. The film with x = 0.2 has a high saturation polarization of 42.3 µC/cm 2 . According to the fitting results, the leakage conduction mechanism is attributed to the combined effect of space-charge-limited conduction mechanism and ionic conduction mechanisms.
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