Author: Patricia Álvarez

A. Queraltó, A. Pérez del Pino, M. de la Mata, J. Arbiol, X. Obradors and T. Puig Crystal Growth and Design 15, 1957-1967 (2015) DOI: 10.1021/acs.cgd.5b00115 The epitaxial growth of Ce_0.9Zr_0.1O_2–y (CZO) thin-films on yttria-stabilized zirconia (YSZ) (001) single crystal and YSZ (001)/stainless steel (YSZ/SS) technological substrates is investigated by pulsed laser irradiation of solution-derived cerium–zirconium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The influence of laser processing parameters on the morphological and structural properties of the obtained films is studied by atomic force and transmission electron microscopies, as well as X-ray diffractometry. The analyses performed demonstrate that laser treatments enable the epitaxial growth of tens of nanometers thick CZO films with a crystallization kinetic process several orders of magnitude faster than that of conventional thermal annealing. Fully epitaxial films are attained using stainless steel (SS) flexible tapes as a substrate. Even though photochemical mechanisms are not fully discarded, it is concluded that photothermal processes are the main contribution responsible for the fast epitaxial crystallization.

P Roura, J. Farjas, H. Eloussifi, L. Carreras, S. Ricart, T. Puig Molina and X. Obradors Thermochimica Acta 601, 1-8 (2015) DOI:10.1016/j.tca.2014.12.016 The thermal decomposition of several metal organic precursors, used in the preparation of YBa₂Cu₃O_7−xsuperconducting coated conductors (Cu acetate, Cu, Y and Ba trifluoroacetates and Ce propionate) is analyzed by means of several thermoanalytical techniques (TG/DTA, MS and DSC). In all cases, the metal organic precursors deposited as thin films decompose differently than powders from the same precursors. In thin films, decomposition is facilitated by the easier transport of reactive gas from the surrounding atmosphere and by the easier out-diffusion of volatile products. Consequently, films decompose at lower temperature and are more sensitive to the presence of any residual reactive gas in the furnace. Good thermal contact with the substrate is also shown to minimize overheating in films and avoid combustion processes that are otherwise often observed during the thermal decomposition of powders. Finally, the formation and stability of intermediate products towards the oxide formation, such as metal fluorides, differs in films because of the easier gas exchange. With respect to powders, these compounds are much less stable in films, where their decomposition temperature can be lowered by several hundreds of degrees Celsius. While in some cases the behaviour of films can be predicted by analyzing varying masses of precursor powders, this is not always the case. Therefore, thermal analysis carried out on films is recommended to avoid erroneous conclusions about materials preparation drawn from powders.