High resolution neutron diffraction patterns of BaCex Zr1−x O3 (x = 0, 0.1, 0.4,0.8) were obtained at various temperatures. The phase diagram that was deduced from Raman measurements has been confirmed. Structural transitions occur in a fixed order Pnma-Imma- R $\bar{3}$ c-Pm3m as a function of temperature or composition. For BaCeO3, the large volume change that has been previously claimed at the Imma-R $\bar{3}$ c transition has been revisited and found inconsistent. For a given composition, the cell volume increases when temperature increases, but the MO6 (M=Ce-Zr) octahedron volume decreases. It is shown that the ratio of the cell volume to the octahedron volume is a good indicator of the phase transitions. Transitions occur at fixed values (5.77, 5.80 and 6 for the Pnma-Imma, Imma-R $\bar{3}$ c and R $\bar{3}$ c-Pm3m transitions respectively) independently of composition.

Barriers of very different character such as localized obstacles and the extendedPeierls- Nabarro relief may control the dislocation motion in crystals in different stressand temperature ranges. The great difference in the microscopic parameters characterizingthese two mechanisms, e.g., in the activation volumes, manifests itself even on themacroscopic scale as a strong change of the plastic properties in a rather narrow transitionrange of the temperature. A theory describing the temperature dependence of the flow stressand the strain rate sensitivity near the transition has been developed and compared withexperimental data on the plastic deformation of cubic ZrO2 single crystals in a softorientation.

we report the growth of BaTiO3 thin films by standard Radio Frequency sputtering. Without any in situ or post annealing, these polycristalline filmsare oriented relative to the substrate even when it is amorphous. We show that thispreferential orientation may be monitored using a DC Bias during the film growth. Atroom temperature, cubic films of (100) and (110) orientations have been achieved, onfused silica substrate. Some optical waveguiding properties of these films have beenstudied. The resulting film index is 2.26 and the optical step index at the substrateinterface is sharp. This allows the use of standard RF sputtering techniques tomonitor oriented BaTiO3 films for linear optical applications.

We have studied Zr1−X CeX O2 film growth on (001) Si by Pulsed Laser Deposition using sputtering of metallic alloy targets and sintered ceramic targets. The conditions of the epitaxial growth have been found and optimized. The epitaxial oxide film growth (001) [100]||(001) [100] Si was obtained for a range of CeO2 content in ZrO2: from 4.5 up to 14% mol in ZrO2. The oxide film structure corresponds to a tetragonal phase with strong preference for c-axis orientation normal to the growth surface. The results obtained by RHEED, XRD and AFM methods have confirmed the high quality of heteroepitaxial Zr1−X CeX O2 layers, and the difference in crystallinities for the films grown from metallic alloy targets and ceramic targets was evaluated. The XRD results show the absence of any reflection distinct from (00l) and (l00) for films grown from alloy targets, and, in contrast with this, the film structure contains some random oriented inclusions in the case of oxide target deposition. Use of metallic alloy Zr-12% Ce targets and low oxygen pressure during deposition provide the best film quality with the minimum of surface microrelief (Rrms <0.3nm for 1 × 1 µm2surface area was achieved).

The evolution of the passivating layer (during the firstreduction/reoxidation cycle, in function of the number of reduction/reoxidationcycles and with the storage of the electrode in the electrolyte) formed at thesurface of a lithiated carbon electrode in LiCF3SO3/carbonates mixture electrolytehas been followed by using 1 MeV 4He+ induced Rutherford BackscatteringSpectrometry (RBS). Two RBS simulation codes "RUMP" and "PERM" , whose approachesare different, have been applied to the treatment of the RBS data and have allowedto obtain informations about the structure (thickness and atomic elementalcomposition) of the passivating layer. These two codes provide similar results. Thepassivating layer has a thickness in the range 20-30 nm. Its structure appears tobe complex with the presence of two different sublayers respectively composed of thereduction products of the salt in the inner sublayer (with the main presence offluorine and sulphur indicating the possible existence of LiF and Li2S) andreduction products of the solvents in the outer sublayer (with a high concentration in oxygen indicating the presence of Li2CO3 and RCO3Li where R is an alkylradical).

Tin disulfide β-SnS2 thin films have been prepared on pyrex substrates bythe spray pyrolysis technique using tin tetrachloride and thiourea as starting materials. Thedepositions were carried out in the range of substrate temperatures from 240 to400 °C. Highly c-axis oriented β-SnS2 films, having a strong (001) X-raydiffraction line are obtained at temperature 280 °C and using concentration ratioin solution $\Re = [{\rm S}]/[{\rm Sn}] = 2.5$ . Films surfaces were analyzed by contactAtomic Force Microscopy (AFM) and by Scanning Electron Microscopy (SEM) in order tounderstand the effect of the deposited temperature on the surface structure. On the otherhand, from transmission and reflection spectra, the band gap energy determined is about2.71 eV. Finally using the photodeflection spectroscopy technique, the thermal conductivityK c and diffusivity D c were obtained. Their values are 10 Wm−1K−1 and 10−5 m2s−1 respectively.

A luminescent study under selective photonic excitation has established thepresence of three different kinds of Ce3+ centres in SrS atomic layerepitaxy thin films: one in a regular sulfur octahedral sites and two others inlower symmetry. These last sites shift the emission spectra towards the green.High thermal annealing up to 750 °C improves the crystallinity of theSrS:Ce layer by converting low symmetry Ce3+ sites in regular octahedralsites and decreasing the density of defects. These two effects lead to efficientPL layers with a good blue chromaticity.

The electromagnetic properties of thin dielectric or composite layersare considered. We study the case when the thickness dof a slab is so small that only a few particles forming the effective medium are located on the interval d. A novel approach to the quasistatic modelling of the local field acting on a particle is suggested.In this casethe local "permittivity" near the upper and lower surfaces of the slab differs from the bulk permittivity of the same material. This can influence the reflection and transmission properties of the slab. Even if the particlesare isotropically polarizable or are randomly oriented in the slab volume, this thin structure has anisotropic (uniaxial) electromagnetic properties.

The optical properties of Ag-TiO2 nanocermet thin films are studied with the aim of optical filtering applications. Beyond the classical properties of cermets with noble metal inclusions predicted by the effective medium theories, the optical properties of Ag-TiO2 nanocermets deposited by R.F. co-sputtering are governed by their columnar morphology and the under-stoichiometry of the TiO2 matrix. A careful experimental analysis of the different parameters and effects involved in the optical response of these nanocermets is performed both on TiO2 and Ag-TiO2: film thickness, silver volume fraction, thermal treatments, oxidation. The influence of these parameters on the surface plasmon resonance and the infrared transmission of the nanocermet thin films is optimized.

Heterogeneous Cox Ag1−x and Nix Ag1−x alloys have giantmagnetoresistance properties. Such alloys, with atomic concentrations x = 0.20 and 0.37,were studied by transmission X-ray Absorption Spectroscopy at the Co or Ni K-edge afterin situ thermal annealing. For alloys as-deposited and annealed at 200 °C,Extended X-ray Absorption Fine Structure analysis displays both Co-Co (Ni-Ni) bonds relatedto Co (Ni) atoms agglomerated in magnetic particles and Co-Ag (Ni-Ag) bonds related to Co(Ni) atoms in substitutional sites in the Ag matrix. At the same alloy concentration, themiscibility in the Ag matrix is found larger for Ni than for Co. After annealing around250 °C, the marked decrease of the Ag neighbour peak corresponds to a diffusion ofmagnetic atoms outside the Ag matrix. The Co-Co coordination number increases regularly withannealing temperatures up to 450 °C reflecting a progressive expansion of Coparticles. On the contrary, for Ni alloys, no further particle expansion has been observedin the same annealing range. This different behaviour may be linked both to the differencebetween the as-deposited structural states and to the Co/Ag and Ni/Ag interfaces energies.Using a simple model, evolution of the mean particle size has been estimated as a functionof annealing.

Mm(OH)3 (Mm = mischmetal) single crystalline needles with [001] growth axis formupon exposure of MmNi5-substituted alloys to aqueous KOH. Crystal structure, chemical composition and morphology of the needles are studied by means of scanning electron microscopy and quantitative transmission electron microscopy. The needles can be either solid (whiskers) or hollow (nanotubes). Their morphology and growth kinetics are studied as a function of immersion temperature, stirring rate of the aqueous KOH electrolyte and presence of tracer. Based on the observations, a model mechanism is developed for their growth.

Dielectric and noise measurements versus frequency have been performed on a liquidcrystal in the paraelectric S A and ferroelectric $S^*_{\rm C}$ phases. A confrontation ofthese measurements is presented on the basis of the fluctuation-dissipation theoremwhich shows that these techniques both give similar results linked to theobservation of the classical soft mode and Goldstone mode in the S A and $S^*_{\rm C}$ phasesrespectively.

Granular Fe-V2O5 thin films with different iron concentrations prepared bymeans of radiofrequency magnetron co-sputtering technique were investigated bymeans of X-ray diffraction, Transmission Electron Microscopy and57Fe Mössbauer spectrometry as a function of iron concentration. A commonexperimental feature reveals that a percolation-like threshold occurs at around23−25% atomic Fe. Below such a critical value, the co-sputtering process favours the presence of ultrafine amorphous oxide grains with sizes lower than10 nm embedded in a vanadium oxide matrix. Above, one clearly observes thepresence of fine grains (sizes comprised between 10−100 nm) composed of eitherhematite or maghemite phases dispersed in the same matrix, the set displaying amagnetic order at room temperature.

A pulse is solution of a boundary-initial value problem for the wave equation.We investigate the propagation in the z-direction of a Maxwell-Hopkinson dielectric of three kinds of pulses launched from the z = 0 plane at some time: harmonic plane wave, Bessel wave, distortion-free progressing wave. We prove that at high frequency, and as soon as the transient state has died out, these pulses propagate with an exponential attenuation factor in the direction of propagation.

The aim of this work is to study the kerosene explosibility in closed or vented vessels and to develop an application to safety systems. The basic characteristics of the model have been developed for the ignition and the combustion of propulsive powders and adapted to liquid fuels with appropriate parameters linked to simplified kinetics. A simple representation of the combustion phenomena based on energy transfers and the action of specific molecular species is presented. The pressure venting, due to the vent breaking is calculated taking into account the mass rate of discharge of the different products in the assumption of the standard orifice equations.The model allows the study of various parameters such as the nature of the kerosene, the fuel ratio of the mixture, the ignition energy, the thermal exchanges and the influence of the pressure venting or the vent area. The theoretical results have been compared with data obtained in the course of experiments performed in small vessel volumes (V 0 = 13 and 33 l) and indicate correct preliminary tendencies.

Diffractive multifocal lenses are usually discussed in terms of geometric zoneprofiles imparted a surface of a refractive lens. Consequently, the zeroth order diffractivepower is usually called the "refractive power" of the diffractive lens. By contrast, wefocuss on the refractive power or refractive power profile of the zones of a diffractivelens and calculate the path length error of any of the zones in a given defocus position onthe lens axis. From this the phase angle of the resulting amplitudes can be calculated.Analytical expressions for the positions of the diffractive powers as a function of (average)zone powers are derived as well as analytical expressions for the intensities in suchpositions. Also, general restrictions on usable zone power profiles are derived.

I-V-T data is routinely used to determine the conduction band discontinuity in heterojunction structures. In the present paper, capacitance-voltage and current-voltage-temperature measurements performed on AlGaAs/GaAs isotype heterojunctions are presented and analysed over a wide temperature range (77 K-300 K). Considering thermionic emission alone when analysing I-V-T data resulted in several problems. The Richardson plot $[\ln(J_0/T^2) vs. 1/T]$ ,in particular while suggesting that the thermally activated process is of importance in the overall conduction mechanism, shows two distinct linear regions of different slope over two temperature ranges. Also the derived activation energies and hence the band discontinuity from I-V-T data is very much lower than the value obtained from C-V profiling which is in very good agreement with values routinely published in literature. However, the results obtained from both I-V-T and C-Vdata are reconciled when considering a simple analytical expression for the current based on the assumption that thermally assisted tunneling is the dominant current generating mechanism over most of the temperature range.

The Dulkyn interferometer in Kazan is an active ring laser where the lightpropagates along two different paths. It has been developed with the ideathat it could detect low frequency gravitational waves on Earth.Considering Dulkyn as a detector of periodic strains of order of h ~ 10−22 at low frequencies (10−3 Hz−10−5 Hz) wecalculate that 30 W is the order of magnitude of the optical powernecessary to beat the photon noise in the case of a long observation time (T = 4 months) and a reasonable signal to noise ratio (r = 3). We estimatethat the displacement noise of the mirrors must not exceed 5×10−19m/ $\sqrt{{Hz}}$ .Dulkyn is also sensitive to accelerations and rotations. The accelerationnoise does not seem to be troublesome ( $\widetilde{g}\lesssim 0.1{m}{s}^{-2}/\sqrt{{Hz}}$ ), but the angular velocity noise must beless than 5×10−11 s−1/ $\sqrt{{Hz}}$ . The maximum strain (10−22) is obtained with free (pendulous) mirrors.Out of resonance, the strain is many orders of magnitude smaller when themirrors are fixed on a rigid support. Such a case would rule out thepossibility of a detection. As a conclusion we emphasize that the Dulkyndesign does not bring any decisive improvement for the detection of lowfrequency gravitational waves on Earth.

We have developed a model for the calculation of the induced current due to an electron beam with anextended generation profile. Added to the absorbed and diffuse electrons in the depth distribution, thegeneration profile takes into account the lateral diffusion. The analytical expression of the electron beam induced current (EBIC) is obtained by solving the continuityequation in permanent regime by the Green function method. The induced current profile, obtained in the case of a ternary component(Ga0.7Al0.3As:N+/Ga0.7Al0.3As:P) sulfur doped and prepared by organometalliccompounds phase vapor epitaxy method, is compared to the theoretical profiles whose analytical expressionsare given by Van Roosbroeck and Bresse. The experimental current profile, measured by S.E.M provided us to calculate the diffusion length of theminority carriers: L p = 1 µm in the N region and L n = 1.80 µm in the Pregion of the ternaire component. The theoretical curve obtained from the proposed model is in goodagreement with the experimental one for a surface recombination velocity of 106 cm s−1. Our resultsare found to be consistent compared to those obtained by other experimental techniques using the samesamples.

A large-core multi mode optical fiber is used to deliver 100 mJ, 5 ns laser pulses produced by a frequency-doubled Nd:YAG laser over a distance of several meters. No damage is observed neither inside the fiber nor at its surface. The transmitted pulses are focused to a diameter of 700 μm onto a water-immersed type 304 stainless steel sample for laser shockprocessing. With a pulse density of 10000 pulses/cm2, a compressive residual surface stressis achieved. The affected depth is almost 900 μm, the maximum compressive stress −700 MPa.