The disordered crystal LiGd 0.936 Yb 0.064 ͑MoO 4 ͒ 2 was grown with high optical quality by the flux method using Li 2 MoO 4 as a solvent. The crystal possesses tetragonal symmetry belonging to the space group I4 , with two nonequivalent sites occupied by the dopant. Spectroscopic studies at 5 and 300 K provided information on the Stark energy-level splitting and the absorption and emission cross sections of the Yb 3+ ion. Laser operation of Yb 3+ was obtained for the first time in such a Li-containing double tungstate or molybdate. The tuning range with a Ti:sapphire laser pumping extended over ϳ32 nm for the polarization and 23 nm for the polarization. Without a tuning element the laser performance was similar for the two polarizations. By using a 10% transmission output coupler, a maximum output power of Ϸ470 mW was obtained with a slope efficiency = 64.5% and the absorbed pump power at threshold was 520 mW. Laser operation was also achieved by pumping with a tapered diode laser and a fiber-coupled diode laser module, with a Yb laser output power of 0.66 W in the latter case.

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Los refractarios de Al 2 O 3 -MgO-C, de gran interés tecnológico por sus excelentes propiedades, se utilizan mayoritariamente en las industrias del hierro y el acero. Estos materiales están constituidos por distintas calidades de corindón, periclasa y grafito a los que se añaden pequeñas cantidades de metales y un polímero que actúa como ligante. En este trabajo establece una metodología para la caracterización química y mineralógica de refractarios de Al 2 O 3 -MgO-C. Los resultados del análisis químico realizado por fluorescencia de rayos X, espectroscopia de emisión de plasma y gravimetría, junto con la información cualitativa acerca de las fases cristalinas (obtenida por difracción de rayos X), y el conocimiento de las materias primas con las que están formulados (obtenido por análisis térmico diferencial y termogravimétrico y microscopia óptica de luz reflejada), se han utilizado para conocer la composición de los refractarios. Los datos obtenidos por las diferentes técnicas dan validez a la metodología desarrollada. Palabras clave: refractarios Al 2 O 3 -MgO-C, microscopia óptica, difracción de rayos X, fluorescencia de Rayos X, espectroscopia de emisión de plasma. Chemical analysis of Al 2 O 3 -MgO-C refractoriesThe Al 2 O 3 -MgO-C refractories, of great technological interest for its excellent properties, are used in a wide range of furnacelining applications such as iron and steel. These materials are composed of various grades of alumina, magnesia, graphite and metallic additives, which are added to a resin that acts as binder. The variety of components oxides, metals and polymers makes the study of these refractories a complex task. Considering this diversity to characterize these materials has been used several techniques: X-ray fluorescence, plasma emission spectroscopy and gravimetry, complemented by X-ray diffraction, differential thermal analysis and thermogravimetry and reflected light optical microscopy. This paper provides a methodology for chemical and mineralogical characterization of these refractory materials. The results of chemical analysis together with the qualitative information on the crystalline phases and the raw materials with which they are formulated have been used to quantify the composition of the refractories using rational analysis. The data obtained by the different techniques validate the methodology developed. Vol 51, 6, 305-312, Noviembre-Diciembre 2012 ISSN 0366-3175. eISSN 2173-0431. doi: 10.3989/cyv.422012 Keywords: Al 2 O 3 -MgO-C refractories, optical microscopy, X-ray diffraction , X-ray fluorescence, plasma emission spectroscopy. Boletín de la Sociedad Española de Cerámica y Vidrio INTRODUCCIÓNDesde los años 80, los refractarios de MgO-C y de Al 2 O 3 -MgO-C (AMC) (1-7) se utilizan cada vez más frecuentemente en las industrias del hierro y el acero, lo que ha dado lugar a una significativa mejora en los procesos metalúrgicos. Más específicamente, los ladrillos de MgO-C se usan como revestimiento en los hornos eléctricos de arco y en línea de escoria de las cuchara...

Magnesia-graphite refractories are currently essential for the iron and steel industry. As a result, their physico-chemical characterization is crucial with a view to predicting their service life. In this work, a methodology for the complete analytical characterization of such materials has been developed. Magnesiagraphite refractories generally contain elemental phases (C, Si, and Al), non-oxide and oxide inorganic phases (SiC, MgO, and Al 2 O 3 ), organic phase (binders), and various additives and impurities. Consequently, their chemical characterization is especially difficult and requires the joint use of the following techniques: X-ray diffraction, differential thermal and thermogravimetric analyses, inductively coupled plasma-atomic emission spectroscopy, flame emission, Fourier transform infrared spectrometry, gravimetry, and C/S elemental analyzer (LECO). The data obtained by the different techniques match satisfactorily and provide validity to the methodology developed. The results obtained for each element analyzed, and the precision of each determination method used, are quite acceptable. J ournal

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