Thermal analysis of metal organic precursors for functional oxide preparation: Thin films versus powders

The thermal decomposition of several metal organic precursors, used in the preparation of YBa2Cu3O7 x superconducting 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.We acknowledge the financial support from MICINN (MAT2011-28874-C02-01 and -02, Consolider Project NANOSELECT: CSD2007-00041), EU project EUROTAPES, (EUFP7 NMPLA2012280432) and by the Generalitat de Catalunya (Pla de Recerca 2009SGR-185, 2009-SGR-770 and XaRMAE). H. Eloussifi acknowledges financial support from the Tunisian Ministry of Higher Education and Scientific Research. The authors are indebted to Dr. Joan Pere López Olmedo and Dr. Xavier Fontrodona of STR, University of Girona, and Dr. Josep Bassas of CCT, University of Barcelona, for their technical assistance.Peer reviewe

Thermal decomposition of barium trifluoroacetate thin films

The thermal decomposition of barium trifluoroacetate thin films under different atmospheres is presented. Thermogravimetry and evolved gas analysis have been used for this in situ analysis. We focus our attention on the different behavior exhibited by films when compared to powders. The decomposition of barium trifluoroacetate is altered due to the faster out-diffusion of the product reaction:CF2. After barium trifluoroacetate decomposition a stable intermediate, barium fluoride, is formed. The decomposition of barium fluoride is diffusion controlled and depends on water partial pressureThis work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2011-28874-C02-01 and MAT2011-28874-C02-02, by the Consolider program Nanoselect, CSD2007-00041, EU project NESPA-RTN and by the Generalitat de Catalunya contracts No. 2009SGR-185 and 2009SGR-77

Thermoanalytical study of the decomposition of yttrium trifluoroacetate thin films

We present the use of the thermal analysis techniques to study yttrium trifluoroacetate thin films decomposition.In situ analysis was done by means of thermogravimetry, differential thermal analysis, and evolved gas analysis.Solid residues at different stages and the final product have been characterized by X-ray diffraction and scanning electron microscopy.The thermal decomposition of yttrium trifluoroacetate thin films results in the formation of yttria and presents the same succession of intermediates than powder's decomposition, however, yttria and all intermediates but YF3 appear at significantly lower temperatures.We also observe a dependence on the water partial pressure that was not observed in the decomposition of yttrium trifluoroacetate powders.Finally, a dependence on the substrate chemical composition is discerned.© 2013 Elsevier B.V.All rights reserved.This work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2011-28874-C02-01 and MAT2011-28874-C02-02, by the Consolider program Nanoselect, CSD2007-00041, EU project EUROTAPES NMP3-LA-2012-280432 and by the Generalitat de Catalunya contract nos. 2009SGR-185 and 2009SGR-77

Thermal analysis of metal organic precursors for functional oxide preparation: thin films versus powders

The thermal decomposition of several metal organic precursors, used in the preparation of YBa2Cu3O7−x superconducting 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 powdersWe acknowledge the financial support from MICINN (MAT2011-28874-C02-01 and -02, Consolider Project NANOSELECT: CSD2007-00041), EU project EUROTAPES, (EUFP7 NMPLA2012280432) and by the Generalitat de Catalunya (Pla de Recerca 2009SGR-185, 2009-SGR-770 and XaRMAE). H. Eloussifi acknowledges financial support from the Tunisian Ministry of Higher Education and Scientific Researc

Solution design for low-fluorine trifluoroacetate route to YBa2Cu3O7 films

We present our work in the preparation of metallorganic precursor solutions with reduced fluorine content, able to fulfil the requirements for high-performance superconducting YBCO epitaxial layers as a promising approach to low cost and scalable coated conductors. Six different solutions using different quantities of fluorine and non-fluorine carboxylate precursors with a total amount of fluorine from 10 to 50% that of standard trifluoroacetic acid (TFA) solutions. For stabilization purposes different coordinating agents have been used and the solution rheology has been modified for proper substrate wettability. Thermal decomposition analysis and infrared spectroscopy performed directly in films, have revealed that the decomposition takes place in two consecutive stages around 265 and 310 °C respectively, and nuclear magnetic resonance (NMR) analysis could unveil the chemical reactions taking place in the solution. Using the solutions with 20% fluorine and upon optimization of the growth process parameters, YBCO layers with T c and J c(77 K) of 90 K and 4 MA cm−2 are obtainedThe authors acknowledge the financial support from MICINN (Consolider NANOSELECT, CSD2007-00041, MAT 2011-28874-C02, MAT2014-51778-C2-2-R); Generalitat de Catalunya (Pla de Recerca 2014-SGR-753 and XaRMAE), and EU (FP7 NMP-LA-2012-280432 EUROTAPES project and MP1201 Cost action