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A novel procedure to make self-supporting thin yttria-stabilised zirconia (YSZ) membranes by laser machining is shown. We have used a galvanometric controlled laser beam to machine the surface of a conventional sintered YSZ plate and achieved thin areas up to 10 lm thick, but also maintaining thicker support beams to ensure the structural strength of the membrane. The outer areas of the plate are left unaltered to facilitate the sealing of the cell. This kind of thin membrane is ideal for preparing electrolytesupported Solid Oxide Fuel Cells (SOFC) operating at intermediate temperatures. The membranes have been characterized by optical profilometry, Raman Spectroscopy and Electrochemical Impedance Spectroscopy. The YSZ properties, except those derived from membrane thinning, remain unaltered by processing. Using the laser machined YSZ electrolyte a conventional electrolyte supported YSZ-Ni/YSZ/LSM-YSZ planar single cell with average electrolyte thickness of less than 50 lm has been fabricated and characterized. Performance of the cell is improved as a result of the thinning process.The Solid Oxide Fuel Cell (SOFC) is one of the key devices for the transformation from the present fossil fuel based economy to a clean economy with zero emission energy use. The core of the SOFC is a solid electrolyte, an ionic conductor at high temperatures. At present, yttria-stabilised zirconia (YSZ) is still the most used electrolyte because of its unrivalled mechanical properties, chemical stability and high degree of knowledge achieved in this material. 1 As a first approach, the solid electrolyte behavior determines the cell performance and operation temperature. In this way, the Area Specific Resistance (ASR) of the electrolyte, defined as the ratio between the voltage drop in the electrolyte and the current density, is one of the main parameters of a SOFC. It is usually considered that this value has to be lower than $0.15 XÁcm 2 to get a cell with good performances. 2 The resistance of a conductor follows the relationshipThe conductivity being r, l the thickness and S the surface of the material. The conductivity of YSZ is a function of the temperature according to an Arrhenius type lawwhere T is the temperature, A the pre-exponential factor, E a the activation energy and k the Boltzmann constant. Since YSZ is a relatively poor electric conductor with E a % 1.1 eV and r (1000 C)3) the direct way to obtain low cell resistance is to prepare the electrolyte as a thin film and/or to operate the cell at high temperatures to get high enough ionic conductivity. Thin electrolytes can be deposited using different techniques such as tape casting, dip coating, spray-painting, etc. over one of the electrodes (either the cathode or the anode) that operate as structural support for the cell. The main advantage of this electrode-supported cell configuration is that very thin electrolytes can be used (usually 10-30 lm) and thus low resistance values are obtained for the most common electrolytes at intermediate temperatures (typically 750-85...

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a b s t r a c tIn this work the fabrication of buried optical waveguides by femtosecond laser inscription in the 0.8CaSiO 3 -0.2Ca 3 (PO 4 ) 2 eutectic glass doped with Nd 3+ ions is reported. The glass samples were prepared by melting the eutectic powder mixture in a Pt-10 wt.% Rh crucible at 1600 • C and pouring it in a preheated brass mould. Afterwards, the glass was annealed to release the inner stresses. Buried waveguides were fabricated by focusing beneath the surface a pulsed Ti:sapphire laser with a pulsewidth of 120 fs working at 1 kHz. Two adjacent parallel tracks were written to define a region where an increase in the refractive index occurs. The effects produced by the variation of the laser pulse energy as well as the lateral separation between tracks, scanning speed and focusing distance were studied. After the laser processing, the near-field intensity distribution at 633 nm of the waveguide's modes was studied demonstrating the confinement of both, the TE as the TM polarizations. In order to diminish the losses induced by colour centres absorption, heat treatments were carried out in the samples. The waveguide's modes were compared with respect to the samples without heat treatments. The spectroscopic properties of the neodymium ions have been characterized to evaluate in what extent their optical properties could be modified by the waveguide fabrication process and to elucidate the potential application of such waveguides as integrated laser sources.

In this work we report the influence of the crystallization stage of the host matrix on the spectroscopic properties of Nd3+ ions in biocompatible glass-ceramic eutectic rods of composition 0.8CaSiO3-0.2Ca3(PO4)2 doped with 1 and 2 wt% of Nd2O3. The samples were obtained by the laser floating zone technique at different growth rates between 50 and 500 mm/h. The microstructural analysis shows that a growth rate increase or a rod diameter decrease leads the system to a structural arrangement from three (two crystalline and one amorphous) to two phases (one crystalline and one amorphous). Electron backscattering diffraction analysis shows the presence of Ca2SiO4 and apatite-like crystalline phases. Site-selective laser spectroscopy in the (4)I(9/2)→(4)F(3/2)/(4)F(5/2) transitions confirms that Nd(3+) ions are incorporated in crystalline and amorphous phases in these glass-ceramic samples. In particular, the presence of Ca(2)SiO(4) crystalline phase in the samples grown at low rates, which has an excellent in vitro bioactivity, can be unambiguously identified from the excitation spectra and lifetime measurements of the (4)F(3/2) state of Nd(3+) ions.

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