The glass bead trade in southern Africa provides important evidence of interregional contact during the early modern period. Compositional analysis of a large assemblage of imported glass beads from the sixteenth- to seventeenth-century AD trading site of Baranda in northern Zimbabwe reveals a south Asian origin of the majority of the beads. Combining stratigraphic data and morphological analysis with innovative compositional XRF and Raman spectroscopy approaches, the research was able to assign the Baranda beads accurately to their correct chronological range. This coincides with the period of Portuguese dominance of Indian Ocean trade.

The proton conducting perovskite MZr1−xLnxO3−δHz ceramics are promising electrolytic membranes for fuel cell and water steam electrolyser applications. Simultaneous elastic/quasielastic and diffraction neutron studies were performed in a wide temperature range (25–1150 °C) on protonated Yb-modified BaZrO3 ceramics: dense (97% of theoretical density) and ultradense (99%) using the triple axis spectrometers. The results allowed us to determine: (i) the real content of bulk protonic species ∼1–5 10−3 mol/mol, (ii) the structural modifications caused by the proton doping, and (iii) the bulk proton dynamics. The quasielastic neutron scattering (QNS) results are discussed in the light of neutron diffraction, conductivity, Raman, thermogravimetric, and thermal expansion measurements. The highest bulk proton motion appears in the temperature range where the structural modifications and the energy activation changes are detected. This allows defining the optimum temperature range for the proton dynamics between 400 and 560 °C.

The various perovskite ceramic electrolytic membranes, (Ba,Sr)(Zr,Ce,Nb,In,Sn)O3 modified by incorporation of Ln/RE elements, are widely investigated due to their high industrial potential for H2 production and CO2 conversion. One of the most important criteria to classify such ceramic as a good membrane is its high mechanical and chemical stability over thousands hours in severe operating conditions: high temperature and (high water) vapour pressure cycling. It is well known that the Ba- and Sr-based materials can easily form the mixed carbonates, hydroxides, hydrates, hydroxycarbonates, … The presence of undesirable phases, even limited to traces, on the ceramic surface, and/or at the grain boundary, may lead directly to the premature degradation. Since such mixed, hydrated, poorly crystallized phases cannot be detected by diffraction experiments, we have performed thermogravimetric analysis as well as IR and Raman spectroscopic study. The comparison of vibrational and TGA signatures characteristic of complex secondary phases i.e. (Sr/ Ba)(OH)x(CO3)y, nH2O and of proton conducting perovskite reveals that the ignorance of a second phase presence can lead to wrong conclusion concerning the bulk proton nature and understanding of associated conductivity mechanisms.

According to the recent hydrogen and methanol economy, the proton conducting materials appear very interesting as an electrolytic membrane and/or an electrode component of fuel cells, CO2/Syngas converters and water steam electrolysers. Prior to the long lifetime requirements their structural and mechanical behaviors as a function of operating condition: high temperature and high water vapor pressure, have to be well determined. Consequently, we designed the autoclave working till 620°C and 50 bars of H2O pressure equipped with a sapphire window allowing in situ Raman scattering measurements. It should be stressed that Raman scattering is an optical technique very efficient to detect both long and short range order structural modifications. The technical and scientific challenges/difficulties encountered during the studies performed on proton conducting zirconates are discussed.

The proton conducting perovskites are widely investigated due to their high potential as electrolyte membranes of fuel cells, water steam electrolysers and CO2/syngas converters. Our comprehensive spectroscopic (Raman, IR, neutron), thermogravimetric, elastic and quasi-elastic neutron diffusion as well as conductivity studies performed on Ln/RE- modified zirconate ceramics with controlled densification (90-99% of theoretical density) reveal the important differences between the surface and bulk protonic species. The results clearly show that trivialization of the protonation process complexity can favorite the adsorption of the surface protonic species (hydroxide, hydrocarbonates, etc), prohibit the incorporation of bulk protons, i.e. species responsible for the proton conduction and confuse the understanding of fundamental aspects concerning the proton conductors such as the true nature of conducting species. Our studies reveal that OH- ions are located at the surface of poor densified ceramic and the bulk conducting protons exhibit an ionic, free of covalent-bonded nature.

Proton conducting ceramics are considered as promising membranes for medium temperature fuel cells, water stream electrolyzers and CO2/syngas converters. Materials for these applications have to be mechanically and chemically stable at corrosive conditions of temperature and water vapor pressure in order to ensure the long life-time operation. Our comprehensive Raman, infrared, thermogravimetric, thermal expansion and neutron diffraction studies have shown that the choice of A and B elements as well as the material processing (synthesis, geometry, density, etc.) are crucial to control aging of material. We will consider an example of BaZr0.25In0.75O3 perovskite to show that several factors such as the carbonation, the traces of secondary AO phases at the grain boundaries as well as the use of samples with highly active surface, i.e. powders or lightly densified ceramics can cause: i) preferential adsorption of surface protonic species such as hydroxides, (hydro)carbonates, water, ii) decreased incorporation of bulk protonic species responsible for the proton conduction, iii) significant modification of the host perovskite structure up to complete crumbling of the material. We will show how to improve potential application of perovskites by understanding and controlling these processes.

The imaging of nanostructural and topological variations on mechanically or chemically aged SiC materials has been performed using non-destructive Raman and Rayleigh μ-spectrometries. The case of a Hi-Nicalonf/(SiC/BN/C)m composite, corroded under alkali and oxidizing environment (modelled using molten NaNO3), is discussed. It is shown for the first time that Rayleigh imaging offers a competitive alternative to AFM measurements for un-prepared, very corrugated surface of materials containing carbon as a second phase. A comparison is made to the analysis of μ-indented areas performed on a polished section of the Ø∼140 μm SCS-6™ Textron SiC fibre. The “smart” Raman images allowed determining the strain distribution within the whole indented area.

PMN(PZN)-PT single crystals exhibit unique electromechanical properties when oriented and poled along the <001> direction. While expensive crystal growth techniques are advancing slowly, it is of great practical importance to develop an alternative low-cost production method based on strongly oriented or textured ceramics. We present here the thermal expansion, dielectric properties and Raman spectroscopy study of Pb(Mg1/3Nb2/3)O3-PbTiO3 solid solution ((1-x)PMN-xPT, 0.2<x <0.4, here after called PMN xPT) single crystals, random ceramics and ceramics prepared by homo-templated grain growth (HTGG) using cubic PMN-PT single crystal seeds as templates and nanoparticles as ceramic matrix. Representative medium to highly textured ceramics were sintered at 1150°C and 1200°C, respectively, and studied by Raman imaging. Raman peak centre of gravity is used to image the x-composition whereas peak intensity is correlated to the unit-cell distortion and related short-range structure. Smart Raman imaging shows that the final composition is very close to that of the matrix. We compare their thermal expansion (-150 to 300°C) and dielectric properties (R.T. to 300°C) with those of corresponding poled or non-poled single crystals and random ceramics homologues. Short-range ordering and phase diagram are discussed.

This work describes the properties of an organic-inorganic hybrid gel with an incorporated I-/I3-redox couple that serves as a solid electrolyte for a dye-sensitized TiO2 photoelectrochemical (DSPEC) cell with an efficiency of 4% [1]. The influence of the AcOH on the hydrolysis and condensation reactions of the gels was studied with the help of infrared spectroscopy, while the presence and the formation of the I3 - species were established from the UV-visible spectra of the gels and independently evaluated from the confocal micro-resonance Raman spectra of the electrolyte encapsulated in the DSPEC during open- and short-circuit conditions. Finally, the same gel electrolyte was used for the construction of an electrochromic (EC) window without a counter electrode with intercalation properties (transmission and reflective configuration).

The problems encountered to tailor simultaneously various specific chemical or physical properties are discussed. Selected polymeric precursors used in association with fine powders allow the control of the nano/microstructure of composites and hence the preparation of functional (FGM) and hierarchical reinforced (HRC) composites, making it possible to combine several kinds of fibers, interphases, and matrices in the same composite (hot microwave absorbent), to control the fiber/matrix interface (long life times composites), to achieve net-shape sintering of 3D composite matrices, and to prepare thick films of metal-ceramic composites with tailored microwave absorption (radar stealthiness).