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Yttrium silicate (Y 2 SiO 5 ) coatings complement SiC coatings for protecting ceramic multilayer composite materials based on carbon-fiber-reinforced SiC composites (C-SiC). Thick (100 m), dense Y 2 SiO 5 coatings were prepared by dip coating, using concentrated aqueous slips. The resulting phases were studied by taking into account the simultaneous presence of oxide and non-oxide materials, which affected the chemical stability of the coatings. Thick, mechanically stable coatings were obtained by sintering in carbon crucibles and a SiC bed in an argon-flow furnace. Pure Y 2 SiO 5 coatings completely separated from the SiC substrates. A high percentage of Y 2 Si 2 O 7 was necessary to fit the thermal expansion coefficients and ensure the stability of the coatings. Oxidation resistance of the coated substrates was investigated by isothermal and stepwise oxidation tests.

Thin films of garnet-type Al-doped Li7La3Zr2O12 (LLZ) are prepared by the sol-gel process. Thin films are prepared on MgO substrates by a dip-coating process using a precursor sol from Zr-alkoxide and Li, La and Al nitrates. After the dip-coating, the dried films are calcined at 450°C to get precursor films. When the precursor films are heat-treated at 900°C in an alumina crucible, La2Zr2O7 is mainly obtained. With coexistence of Li2CO3 powders in the crucible during the heat-treatment at 900°C, thin film of polycrystalline cubic LLZ is obtained. Addition of an ionic surfactant, lithium dodecylsulfate, improves the quality of the thin films, and the thin film heat-treated at 900°C with coexistence of Li2CO3 powders in the crucible shows the ionic conductivity of 2.4×10-6 S cm-1 at 25°C.

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Organic/inorganic hybrid membranes based on (3-glycidoxypropyl) trimethoxysilane (GPTMS) and ethylene glycol diglycidyl ether (EGDE), have been prepared by sol-gel method and organic polymerization as solid electrolytes for Li-ion batteries. Lithium bis(trifluoromethane)sulfonamide (LiTFSI) was used as Li salt. FTIR and Raman spectroscopies were used to confirm the hybrid structure formation and the interactions between Li ions and hybrid network. An Arrhenius-like temperature dependence of ionic conductivity was observed for solid hybrid electrolyte membranes, suggesting that the diffusion of charge carriers was assisted by the segmental motions of the organic network. The Li-ion transfer number was determined and correlated with their ionic conductivities. Maximum ionic conductivities for the solid hybrid electrolyte membrane with LiTFSI and a [Li + ]/[O] = 0.10 (class II hybrid) of 1.1 10-5 S/cm was obtained at room temperature. A good value of electrochemical stability window (7 V) and an excellent high rate performance after 500 cycles make these hybrids materials a promising electrolyte candidate for all-solid-state lithium battery applications.

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