RAFAEL MORGADO BATISTA
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Artigo IPEN-doc 28882 Phase transformation/stabilization and ionic conductivity in tantalum oxide co‑doped zirconia‑scandia solid electrolyte2022 - SOUZA, J.P.; FUJIMOTO, T.G.; BATISTA, R.M.; STEIL, M.C.; MUCCILLO, R.; MUCCILLO, E.N.S.The influence of small amounts of tantalum oxide as co-dopant on phase transformation and stabilization, microstructure and ionic conductivity of zirconia-10 mol% scandia is reported in this work. Cylindrical pellets were prepared by solid state synthesis with sintering at 1500 °C for 5 h. High relative density values (> 95%) were achieved. Reduction of the enthalpy for the cubic ⇌β-rhombohedral phase transformation was found for increasing amounts of the co-dopant. Full stabilization of the cubic structure at room temperature was obtained with only 0.45 mol% tantalum oxide addition. The ionic conductivity of sintered specimens was investigated as a function of the temperature and oxygen partial pressure by impedance spectroscopy. The fully stabilized co-doped system revealed a pure ionic conduction behavior up to 800 °C with wide electrolytic domain. In the 700–800 °C range, the ionic conductivity of co-doped specimens is similar to that of pure zirconia-scandia.Artigo IPEN-doc 25823 Sintering evaluation of doped lanthanum gallate based on thermodilatometry2019 - BATISTA, R.M.; REIS, S.L.; MUCCILLO, R.; MUCCILLO, E.N.S.The sintering behavior of La0.9Sr0.1Ga0.8Mg0.2O3-δ oxide-ion conductor was systematically investigated by thermodilatometry. The shrinkage data obtained with heating rates of 4, 7, 10 and 12 °C min−1 were analyzed by the constant rate of heating model and by construction of the master sintering curve. Validation of the master sintering curve was carried out by measurements of density in conventionally sintered specimens. Slight anisotropy of shrinkage data was found and changes to the basic equation of density was proposed to account for this effect. Plotting the data determined by the constant rate of heating model versus density allowed an easy identification of the density range of constant activation energy. The activation energy (865 kJ mol−1) obtained from the master sintering curve correlates quite well with that (874 kJ mol−1) obtained by the constant rate of heating model.Resumo IPEN-doc 25404 Análise por dilatometria do processo de sinterização do condutor iônico La0,9Sr0,1Ga0,8Mg0,2O3-d2018 - MUCCILLO, E.N.S.; REIS, S.L.; BATISTA, R.M.; MUCCILLO, R.Compostos cerâmicos com estrutura perovskita à base de LaGaO3 contendo substituições parciais por Sr e Mg nos sítios A e B, respectivamente, apresentam elevada condutividade de íons oxigênio e são candidatos como eletrólitos sólidos em células a combustível de óxido sólido. A sinterização destes condutores iônicos é, em geral, realizada em altas temperaturas, resultando em perda de Ga e conseqüente formação de fases não-condutoras. Neste trabalho o processo de sinterização do composto La0,9Sr0,1Ga0,8Mg0,2O3-d foi investigado pelos métodos da taxa constante de aquecimento e pela construção da curva mestra de sinterização, empregando dados de dilatometria. O principal objetivo foi avaliar a evolução da sinterização desta cerâmica preparada por reação em estado sólido, em tratamentos térmicos arbitrários. A análise dos dados de dilatometria permitiu obter a energia aparente de ativação (~865 kJ/mol), além de prever a evolução da densidade durante a sinterização não-isotérmica por meio da construção da curva mestra.