No abstract

Ceramic materials formed by complex metal oxides are assuming a very important role on the scientifically and technological development. The synthesis by reaction of combustion is of particular interest once it is a very quick and cheap method to obtain products with both levels of purity and excellent reproducibility. The method is based on a highly exothermic reaction that provides the necessary energy for the chemical transformation and the obtaining of reasonable ceramic products. This result must be confirmed by JCPDF 52-0279 chart, obtained products are monophasic. The present work aims to synthesize and characterize the Zn 0,5 Ni 0,5 Fe 2 O 4 in order to relate the micro-structural properties. The analysis of the thermal treatment effect generates a duplication of the crystallinity values related to material. The thermal treatment leading to a rising of the crystallinity of sample confirmed by the crystallite size of 422.4nm.

INTRODUÇÃOMateriais luminescentes são bastante conhecidos há um certo tempo, e eles foram estudados bastante, não só do ponto de vista científico, como também para seu potencial de aplicação tecnológica, como, abajures fluorescentes, imagens médicas de raios X, tomógrafo computadorizado, entre outras aplicações. Durante décadas passadas, a luminescên-cia dos materiais cerâmicos era extensivamente estudada em materiais cristalinos, em baixas temperaturas [1].O desenvolvimento de materiais semicondutores, com propriedades ópticas ativas como fotoluminescência (FL), eletroluminescência, ou propriedades ópticas não lineares pode conduzir a novos dispositivos com desempenho superior ou a diferentes modos de atuação [2,3]. Neste sentido, tem havido atualmente um interesse muito grande, no estudo da FL, em materiais amorfos ou materiais não estruturados. Isso é confirmado pelo intenso esforço de pesquisa, que vem sendo feito no estudo de vários tipos de FL visível, em temperatura ambiente, como por exemplo, o silício poroso [4]. Recentemente, foi desenvolvido o estudo de materiais desordenados, apresentando intensa fotoluminescência de emissão na região do visível à temperatura ambiente. Foi estudada [5] a fotoluminescência em sistemas amorfos de TiO 2 -PbO, e verificaram que pela adição de Pb na estrutura amorfa, acontece um aumento no grau de desordem, e isso

Cerium oxide has a high potential to be apply in removing pollutants combustion powders, organic materials from waste water and in the technology of fuel cells. Nickel oxide is an attractive material due to its excellent chemical stability, and their optical, electrical and magnetic proprieties. In this work, CeO2-NiO systems on molar ratios of 1:1, 1:2 and 1:3 citric metal-acid were synthesized by using Pechinis method. The change in compositions and calcined temperature were studied by different techniques such as: XDR and SEM. It was also done a microstructural study by Rietvelds method, whose routine was designed to run in the Fullprof Suite program, and analyzed by pseudo-Voigt function. It has noticed that the molar ratio between metal-citric acid in the system CeO2-NiO 1:1, 1:2 and 1:3 has a strong influence on microstructural proprieties, crystallite size and cell micro-deformations and can be used to control these proprieties.

This paper presents the synthesis, characterization and influence of oxidizing atmosphere in the calcinations and sintering processes on microstructural properties of mixed oxides of Cerium and Zinc, obtained by the polymeric precursor method, aiming at a subsequent catalytic application. The material was submitted to calcinations and sintering at 900 and 1050 °C. The samples were characterized by XRD analysis techniques, surface area by BET method and refined by the Rietveld method. The results of X-ray diffraction showed that interest phase was formed, indicating that the method for obtaining the phase is effective. The results of surface area for the system calcined in air were 85 m2/g and 65 m2/g for the system subjected to oxidizing atmosphere both at 900°C, in the same temperature. It was observed that the temperature increase leads to an increase in crystallite size. This fact is in line with other studies in the literature.