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In this work, a procedure to elaborate a homogeneous sunspot area series using the Royal Greenwich Observatory/USAFINOAA data (from 1874 to the present) and the De la Rue and co-workers data (from 1832 to 1868) is presented. These two data series correspond to time intervals that do not overlap and a direct comparison between them could not be carried out. We used the International Sunspot Number (Ri) and the Group Sunspot Number (RG) as a link between the two original series. Thus, two homogeneous sunspot area series have been built using a simple mathematic procedure based on linear relations. [ABSTRACT FROM AUTHOR]

The deconvolution of X-ray diffraction profiles is a basic step in order to obtain reliable results on the microstructure of crystalline powder (crystallite size, lattice microstrain, etc.). A procedure for unfolding the linear integral equation h = gf involved in the kinematical theory of X-ray diffraction is proposed. This technique is based on the series expansion of the 'pure' profile, f. The method has been tested with a simulated instrument-broadened profile overlaid with random noise by using Hermite polynomials and Fourier series, and applied to the deconvolition of the (111) peak of a sample of 9-YSZ In both cases, the effects of the 'ill-posed' nature of this deconvolution problem were minimized especially when using the zero-order regularization combined with the series expansion. [ABSTRACT FROM AUTHOR]

Two pieces of as-sintered 3mol% yttria tetragonal zirconia polycrystals were joined and the electrical response of this composite was compared with the one of its counterparts. The joined sample showed higher electrical conductivity than the assintered sample. This effect was attributed to the joining process.La respuesta eléctrica de la unión superplástica de dos muestras de 3mol% Y-TZP ha sido comparada con la de una muestra sin unir. La muestra unida presenta una conductividad eléctrica mayor que la muestra sin unir. Este aumento de conductividad se atribuye al proceso de unión.

Accurate X-ray quantitative analysis in SiC-based ceramics is a difficult task owing to the strong overlap among the Bragg reflections of the different polytypes. In relation to this point, the Rietveld method can be used as a powerful tool in order to solve this problem. In this study we have applied this procedure to determine the weight fractions of the phases in a liquid– phase-sintered SiC sample. It is shown that the consideration of preferred orientation effects is also indispensable to obtain the accurate proportion of the phases.La determinación de las fracciones en peso de las fases mediante difracción de rayos X es enormemente complicada en cerámicos a base de SiC debido al intenso solapamiento entre las reflexiones Bragg de los diferentes politipos. No obstante, el método de Rietveld constituye una herramienta poderosa para resolver este problema. En este trabajo se utiliza el método de Rietveld al objeto de determinar las fracciones en peso de las diferentes fases para una muestra de SiC sinterizado en fase líquida (LPS SiC). Nuestros resultados ponen también de manifiesto la necesidad de incorporar correcciones debidas a orientación preferencial para efectuar un análisis cuantitativo preciso.

The evolution of microstructure and electrical behaviour of nanocrystalline ZrO2 - 3mol% Y2O3 samples with respect to thermal cycles have been investigated. The sample, that initially consisted of 77.8%wt of tetragonal and 22.3%wt monoclinic phases, eliminates the tetragonal phase by means of a low temperature t-m phase transformation in which the content of monoclinic phase reaches 96%wt. This transformation affects significantly the electrical properties of the sample, increasing the grain boundary resistivity in successive thermal cycles, whereas the bulk contribution remains unchanged. The growth of the grain boundary resistivity is believed to be due to the presence of microcracks that accommodate the larger size of monoclinic grains.Se ha estudiado la evolución con los tratamientos térmicos de la microestructura y el comportamiento eléctrico de nanocristales ZrO2 - 3mol% Y2O3. La muestra, que inicialmente estaba compuesta por 77.8%wt de fase tetragonal y 22.3%wt de fase monoclínica, sufre una transformación de fase t´m a baja temperatura en la que el porcentaje de fase monoclínica alcanza el 96%wt. Esta transformación afecta significativamente a las propiedades eléctricas del material de forma que la contribución del borde de grano ve incrementada su resistividad en los sucesivos ciclos térmicos, mientras que la contribución del grano no cambia significativamente Creemos que el aumento de resistividad del borde de grano esté relacionado con la aparición de microfisuras que acomodan el mayor tamaño de los granos monoclínicos.

In this work, we propose a polymorphic method for the quantitative analysis in zirconia. This procedure uses a square system of equations relating the intensities of a peaks groups set in the diffraction pattern with the weight fractions of the different phases present in the sample. In this system it is used as unknowns, besides the relative abundance of the phases, a group of parameters that incorporates the contribution from the tails of the groups adjacent to the intensity of a selected group. The described procedure has been applied to a simulated diffractogram corresponding to a composition of zirconia of 50% of cubic phase, 25% of tetragonal phase and 25% of monoclinic phase, and also to a sample of zirconia processed by the sol-gel method.En este trabajo se propone un método polimórfico para el análisis cuantitativo de fases en la circona. Este procedimiento emplea un sistema de ecuaciones compatible y determinado que relaciona las intensidades de un conjunto de grupos de picos del espectro de difracción con las fracciones en peso de las diferentes fases presentes en la muestra. En dicho sistema, además de las abundancias relativas de las fases, se utilizan como incógnitas un conjunto de parámetros que dan cuenta de la aportación de las colas de los grupos de picos adyacentes al grupo de picos considerado. Este procedimiento se ha aplicado a un difractograma simulado correspondiente a una circona con 50% de fase cúbica, 25% de fase tetragonal y 25% de fase monoclínica y también a una muestra en polvo de circona fabricada mediante técnicas sol-gel.