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| Author(s): |
Carlos Augusto Escanhoela Júnior
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2015-05-07 |
| Examining board members: |
Valmor Roberto Mastelaro;
José Antonio Eiras;
Santiago José Alejandro Figueroa;
Maximo Siu Li;
Marcelo Ornaghi Orlandi
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| Advisor: | Valmor Roberto Mastelaro |
| Abstract | |
The perovskite structure materials comprise a large group of compounds with the structure in simple form can be represented by the ABO3. chemical formula. The main advantage that the perovskite structure presents is the high degree of flexibility to accommodate a wide variety of atoms in sites A and B, allowing a greater control of physical and chemical properties of the material, maintaining its structure even for a high concentrations of substituent\'s. Due to these properties, these materials have been successfully applied as capacitors, varistors, photoelectrodes, ferroelectric memories and gas sensors. In the last decade, strontium titanate (SrTiO3, ST) in the form of thin and thick films have been reported as oxygen gas sensor at higher temperatures (> 500 °C). Recently, strontium titanate doped with Fe was used as the first ozone sensor. However, the work was carried out only with a certain composition and some important properties for this application have not been fully exploited. In this context, this PhD thesis aimed to the synthesis of strontium titanate system in powder form and nanostructured thin films with the substitution of Sr for La and Ti for Fe. In order to verify the effect of these substitutions in material properties initially Sr1-xLaxTiO3 (SLT) samples were prepared in powder form by the polymeric precursor method in order to evaluate the influence of the addition of La in the structure of the compound ST. Subsequently, samples were synthesized from SrTi1-x Fex O3 (STF) and Sr1-XLaxTi1-yFeyO3 (SLTF) systems through the polymeric precursors, which were used for the deposition of thin and thick films, which were respectively obtained through electron beam deposition techniques (EBD) and spin-coating (SC). Samples in the form of nanostructured powder and thin films were characterized by X-ray diffraction, X-ray absorption spectroscopy (XANES) at Ti and Fe K-edges and by X-ray photoelectron spectroscopy (XPS). Morphological analysis was performed using the scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The STF and SLTF samples in a thin film form were evaluated towards their sensitivity to O3, NO2, NH3 and CO gases. The results indicated that SLTF films deposited by electron beam deposition technique exhibit higher sensitivity to ozone gas. However the same composition deposited by spin-coating showed a better stability and recovery time relative to the same gas. (AU) | |
| FAPESP's process: | 10/20582-6 - Synthesis and Characterization of Sr1-xAxTi1-yByO3 (A = La, B = Fe, W)Nanostructured System : Application as Gas Sensor |
| Grantee: | Carlos Augusto Escanhoela Júnior |
| Support Opportunities: | Scholarships in Brazil - Doctorate |