Hybrid Chemical Vapor Deposition/Sol-Gel Route in the preparation of nanophasic LaCoO3 films

Lanthanum cobaltite (LaCoO3) thin films were synthesized by an innovative route based on the combination of chemical vapor deposition (CVD) and sol-gel (SG) methods. In particular, the approach is based on the sequential deposition of binary oxide systems (Co-O on La-O) and on the ex situ thermal treatment of the final product (T = 400-900 °C, t = 1-8 h), aimed at favoring solid-state reactions for the formation of a ternary La-Co-O nanosystem. To highlight the peculiar effects of these procedures on the characteristics of the final product, both SG and CVD routes were used for the preparation of single-phase La-O and Co-O species. The process resulted in the formation of LaCoO3 nanostructured films with an average crystallite size lower than 20 nm. The required processing conditions were strongly dependent on the specific synthetic pathway: (i) SG of Co-O on CVD La-O; (ii) CVD of Co-O on SG La-O. In this framework, particular attention was focused on the analogies and differences between the two sequences and on a study of the most relevant compositional, structural, and morphological system features.