Browsing CAP - Indexed Articles in Journals by Author "A. Almeida"
Results Per Page
ItemSol-gel reaction stability studied: Influence in the formation temperature and properties of ferroelectric thin films( 2009) Javier Cruz ; P. M. Vilarinho ; A. L. Kholkin ; A. AlmeidaLead zirconium titanate (PZT) sol-gel solutions were prepared based on distilled lead acetate precursor solutions. A detailed analysis of the distillation effect on the lead precursor and the final PZT solution were carried out by Infrared and Raman techniques. It was found that the increase in the number of distillation steps experienced by the lead precursor solutions removes the constitutional water and increases the lead acetate-2-methoxyethanol interconnectivity; thus improving stability and avoiding the aging effect of the resulting PZT solutions. The thermal decomposition process of the PZT solutions was analyzed based on the thermogravimetric (TG) and differential thermogravimetric analysis (DTA) measurements. It was found that as the number of distillation steps in the lead precursor solutions increases, the decomposition rate increases and the formation temperature of pure perovskite PZT films decreases. X-ray diffraction (XRD) technique was used to study the film phase formation. A pure perovskite phase at 500 8C was found by the XRD analysis after the second distillation step. Scanning electron microscope technique was used to carry out the microstructural analysis. Dense microstructure was found in all analyzed films and an incipient columnar grain growth was revealed in PZT films prepared based on lead precursor solution with more than three distillation steps. The dependence of the dielectric, ferroelectric and piezoelectric properties on the number of distilla
ItemSpin-phonon coupling and magnetoelectric properties: EuMnO3 versus GdMnO3( 2009) W. S. Ferreira ; L. G. Vieira ; J. L. Ribeiro ; J. Kreisel ; P. S. Carvalho ; T. M. Mendonça ; M. A. Sá ; J. M. M. da Silva ; J. B. Oliveira ; J. P. Araújo ; M. R. Chaves ; A. Almeida ; J. A. Moreira ; Sérgio Mendonça ; P. B. Tavares