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Nanostructured lanthanum cobaltite thin films have been grown on silica substrates by hybrid chemical vapor deposition/sol-gel approaches. The refractive index and the extinction coefficient of the specimens have been determined in the spectral range of 0.75-6.5 eV by spectroscopic ellipsometry. The conductivity of the films as a function of temperature has been also investigated, highlighting the different electrical behavior of LaCoO3 nanosystems as a function of the adopted synthetic strategy.

This work is focused on the sol-gel synthesis of pure and Ca-doped LaCoO 3 nanopowders. The samples were prepared starting from methanolic solutions of cobalt (II) acetate (Co(CH 3 COO) 2 . 4H 2 O), lanthanum (III) nitrate (La(NO 3 ) 3 . 6H 2 O) and calcium (II) acetate (Ca(CH 3 COO) 2 . H 2 O). After solvent evaporation, the obtained powders were dried under vacuum and subsequently treated in air up to 1273 K. The system evolution under thermal annealing was studied by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), while the chemical composition was analyzed by X-ray Photoelectron (XPS) and X-ray Excited Auger electron (XE-AES) spectroscopies. The temperature and field dependence of the magnetic properties of the Ca-doped samples were investigated, and compared to those of the corresponding pure LaCoO 3 powders. INTRODUCTION Perovskite-type oxides of rare-earth and transition metals (LaMO 3 , M = Co, Mn, Fe…) are being increasingly investigated due to their potential applications in heterogeneous catalysis, oxygen sensing and Solid Oxide Fuel Cells (SOFCs) [1]. Among them, lanthanum cobaltite is particularly promising, thanks to the accessibility for cobalt of the II and III oxidation states. Furthermore, the partial substitution of lanthanum by strontium and calcium improves the material functional properties