V. M. Orera

Conductivity anisotropy in directionally solidified CaZrO3CaSZ and MgO-MgSZ eutectics

The results of the impedance spectroscopy measurements on eutectic samples based on zirconium oxide are presented here. Samples of CaZrO3ue5f8ZrO2(cubic) and MgOue5f8ZrO2(cubic) have been grown by a directional solidification procedure such that the different phases appear nearly oriented along the growth direction (lamellae in the system of CaZrO3-ZrO2(cubic) and fibers of MgO in a ZrO2 matrix in the other system). The DC electrical conductivity has been measured by impedance spectroscopy along and across the growth axis. For CaZrO3ue5f8ZrO2 the coductivity is clearly anisotropic. The following values for σT have been obtained: the conductivity at 600 °C equals 2.0 × 10−6 Ω−1 cm−1 perpendicular to the fiber axis and 1.4 × 10−5 Ω−1 cm−1 parallel to it and with an activation energy of 1.3 eV for σT. For MgOue5f8ZrO2(cubic) the isotropic value of the conductivity at 600 °C is 10−4 Ω−1 cm−1 with activation energy for σT of 1.5 eV. The anisotropic conductivity in the CaZrO3ue5f8ZrO2 (cubic) system has been explained by a model of an ordered stacking of oxygen conducting (cubic ZrO2) and non-conducting (CaZrO3 or MgO) phases.

Microstructure-size dependence of the 1.520 μm Er3+ luminescence lifetime in Al2O3-ZrO2 eutectic melt growth composites

The radiative lifetime of the 4I13/2 level of Er3+ was modified up to 15% by changing the microstructure in laser-floating-zone-grown Er3+-doped Al2O3–ZrO2 eutectic melt growth composites. Erbium enters only the higher-refractive-index ZrO2 phase, which occupies 30% of the volume of the sample. The lifetimes of 4S3/2 (545 nm) and 4I13/2 (1520 nm) Er3+ levels were measured at 10 K and room temperature in different microstructures. The variation in the lifetime of this last level with interphase spacing is due to the change of the available electromagnetic modes at 1520 nm due to the change in the optical environment of the luminescent ion.

Polymer matrix synthesis of zirconia eutectics for directional solidification into single crystal fibres

Abstract ZrO 2 /CaO composites were synthesized by addition of PEI to an aqueous solution of zirconium and calcium acetates. The formed precomposite gel was converted to ZrO 2 /CaO composite on further sintering. The composite powders thus obtained were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and infra-red (IR) spectroscopy. Single crystal fibres were grown from these composite powders by the laser floating zone (LFZ) technique at varying growth rates. The resultant fibres revealed laminar-type eutectic structures and the relative phase alignment was found to depend on the LFZ growth conditions. These fibres were further characterized by Raman spectroscopy and conductivity measurements.

Tetragonally distorted Cr2+ ions in BaF2 and SrCl2 studied by ESEEM spectroscopy

Electron spin echoes on tetragonally distorted non-Kramers Cr2+ ions in chromium doped BaF2 and SrCl2 single crystals have been observed. The superhyperfine interaction (shf) with the nearest halide ions has been studied using the electron spin echo envelope modulation (ESEEM) signal. For Cr2+ in BaF2 the nearest coordination shell consists of four equivalent fluorine ions in a plane perpendicular to the defect tetragonal axis, the Cr2+ ion being off-centre displaced towards the fluorine plane. The Cr2+ shf tensor for BaF2 has been determined. For SrCl2:Cr ESEEM signals associated to the shf interaction with nearest chloride ions were observed but the measurements did not allow us to give a definitive defect model in this case.

Microestructura y propiedades mecánicas de fibras cerámicas eutécticas Al2O3/Er3Al5O12/ZrO2 procesadas por fusión zonal por laser

Resumen del trabajo presentado a la IV Reunion de Jovenes Investigadores en Coloides e Interfases, celebrada en Cordoba del 7 al 9 de febrero de 2018.Trabajo financiado por los proyectos SEROS (CGL 2014-55900-PL), DR3AM (CGL2015- CGL2014-55118) y Grupos Geotransfer y Analisis de Cuencas de la Universidad de Zaragoza. Es una contribucion del Institut de Recerca Geomodels y del Grup de Geodinamica i Analisi de Conques (2014SGR467).Resumen del trabajo presentado a la I Jornada de jovenes investigadores de ceramica y vidrio en el ICMA, celebrada el 20 de marzo de 2018 en la Universidad de Zaragoza.Gracias a todas las instituciones y organismos que han hecho posible este trabajo: al Ministerio de Economia y Competitividad por la beca FPI enmarcada en el proyecto MAT2011-22719, a la Universidad de Zaragoza y al Instituto de Ciencia de Materiales de Aragon.577 Pags.- Figs.- Tabls.- Fots. El contenido de los apartados que componen este libro es de exclusiva responsabilidad de los autores. Creative Commons License Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)Angel Larrea and Sonia Serrano-Zabaleta acknowledge funding from project MAT2012-30763 and the use of Servicio General de Apoyo a la Investigacion-SAI, Universidad de Zaragoza.Trabajo presentado al 8th International UHMWPE Meeting, celebrado en Torino (Italia) del 19 al 20 de octubre de 2017.Trabajo presentado al XI Congreso Nacional de Materiales celebrado en Zaragoza del 23 al 25 de junio de 2010.