The powder indexing method based on successive dichotomies is considered in terms of partition of volume space. With this strategy, the smaller and more probable solutions are found first. Two approaches are described; if density and molecular weight are introduced, the calculations are accelerated. Extension of the method to the monoclinic case is described, and can be useful for unit cells with not too large volumes. A program, DICVOL, has been written in Fortran which allows a search for systems down to monoclinic.

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Tese apresentada como parte dos requisitos para obtenção do Grau de Doutor em Ciências na Área de Tecnologia Nuclear -Materiais Orientadora: Dra. Emília Satoshi Miyamaru Seo SÃO PAULO 2012 Dedico este trabalho ao meu pai Francisco Vargas Maldonado Filho, à minha mãe Lizete Azevedo e ao meu irmão Renato Azevedo Vargas, por tudo que significam e por todos os valores que me ensinaram. Dedico também à minha noiva Giovanna Toschi Bambicini, pelo seu amor, carinho e compreensão.

Modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and X-ray diffraction were used to study the phase transitions in single crystals of KHSO 4 (KHS) above room temperature. Our results show three phase transitions, on heating a freshly prepared sample: the first one at %120 C (exothermic and metastable) accompanied by small weight loss (less than 0.25wt%), the second one at %178 C (endothermic) and the third one at %212 C (endothermic, melting point). The latter two phase transitions are also accompanied by weight loss and its rate depends on the surface of the sample. We discuss the first transition in terms of absorbed water molecules weakly bound to the surface that are released at 120 C on heating a fresh crystal from room temperature. The second transition at 178 C is discussed in terms of a partial polymerization setting in at reaction sites distributed on the surface of the crystals followed by the final decomposition above 212 C.

The (La0.60Sr0.40)(Co0.20Fe0.80)O3-δ - LSCF, (Ce0.90Gd0.10)O1.95 - CGO composites and LSCF were deposited by wet powder spraying deposition method for the purpose of investigating their potential use in Intermediate Temperature Solid Oxide Fuel Cells. The interlayers are necessary between CGO electrolytes and LSCF cathodes in order to improve the performance of these materials. LSCF particles synthesized by citrate technique were calcined at 900 °C for 4 h and, their LSCF-CGO composites and LSCF suspensions deposited on CGO substrate and, sintered in 1100 °C for 1 h, were formed pseudo-perovskite. The ceramics materials were analyzed by X-ray diffraction (XRD) and chemical composition of different half-cells layers by scanning electron microscope with energy dispersive (SEM-EDS). The results are in agreement with the literature and indicate that route studied is adequate for crystal structures formation compatible with films the 35 µm thick total for study of conductivity between the cathode and the electrolyte.