Claude Lucat

Critical review of nitrogen monoxide sensors for exhaust gases of lean burn engines

Abstract The paper intends to establish a comprehensive state of the art of nitrogen monoxide sensors applicable to the exhaust gas of lean-burn engines. The drastic operating conditions imply similar requirements to the oxygen lambda gauge. To date, like for oxygen sensing, only solid electrolyte- and semiconductor oxide-based sensors can be considered for NO sensing. The results of an exhaustive literature search on these types of sensors permit to propose some directions of research, taking into account principles, materials and manufacturing technologies.

Etude par diffraction de neutrons de la solution solide Pb1−xBixF2+x: Correlations entre structure et conductivité ionique

Bragg neutron diffraction studies have been carried out on the fluorite-type solid solutions Pb 1− x Bi x F 2+ x (0≤ x ≤0.50). The distribution of fluorine atoms between normal and interstitial sites as a function of the substitution rate is determined. Electrical and structural data are correlated. These results are compared with those obtained from the Ca 1− x Y x F 2+ x solution.

Longitudinal vibration mode of piezoelectric thick-film cantilever-based sensors in liquid media

We report on the fabrication of a self-actuated resonant-microsensor, based on a thick-film piezoelectric cantilever, dedicated to either (bio)chemical detection in gaseous or liquid media or fluid characterization. The aim of this paper is to demonstrate that longitudinal modes can be used in highly viscous environments. Lower levels of fluid-solid interaction in comparison with classical flexural modes are expected from the results of our analytical model of a cantilever oscillating in a fluid. For example, in various fluid ranging from air to a Newtonian fluid of 300 cP viscosity, measured quality factors for the first longitudinal mode range from 300 to 20.

Etude des proprietes structurales et electrioues d'un nouveau conducteur anionique: PbSnF4

Three allotropic varieties of PbSnF4 - α, β and γ - have been detected by DTA and X-ray diffraction. The α ai β and β ai γ transitions are reversible and occur at 80 and 355°C respectively. The high temperature form γ - PbSnF4 is cubic and of fluorite type. The structures of the tetragonal β - PbSnF4 and the orthorhombic α - PbSnF4 forms are derived from the same structural type. PbSnF4 has a high anionic conductivity (σ200°C ⋍ 10−1 Ω−1cm−1). The temperature dependence of the conductivity indicates the existence of a break in the activation energy at 90°C.

Sur de nouveaux conducteurs anioniques de hautes performances

The study of ionic conduction in fluorides with fluorite type structure leads to new anionic superconductors of formulation Pb1−xBixF2+x (0 ⩽ x ⩽ 0.50). The strong polarizability of the Pb2+ and Bi3+ cations gives a highly conducting material. In particular Pb0.75Bi0.25F2.25 has a conductivity close to that of β-alumina.

Synthese et etude des proprietes de conductivite ionique des phases appartenant aux systemes KBiF4 BiF3 et RbBiF4 BiF3

Resume Two solid solutions K1−xBixF2x+1 (0.50 ⩽ x ⩽ 0.70) and Rb1−xBixF2x+1 (0.50 ⩽ x ⩽ 0.60) and two homologous KBi3F10 and RbBi3F10 (x = 0.75) phases have been obtained. Electrical and structural data are correlated.

About the allotropic transformations of PbSnF4

Abstract Microcalorimetric and dilatometric studies of PbSnF 4 give evidence of several allotropic forms for PbSnF 4 . The complex thermal behaviour may be summarized as follows : . The crystallographic data of the detected allotropic forms have been determined by investigations on single crystals. All structures derive from the fluorite-type. The obtained results confirm a previous work of the authors, new more precise techniques bringing further information.

Ionic conductivity of fluorite-type fluorides

Abstract A review is given of our last results in the field of fluoride-ion conductors with fluorite-type (or related) structure. The results obtained are discussed. PbSnF 4 is the best anionic conductor so far known thanks to strong cationic polarizability. Some electrochemical applications are proposed.

Etude des proprietes de conductivite anionique des solutions solides Pb1−xThxF2+2x

Abstract Two solid solutions Pb 1−x Th x F 2+2x of fluorite and of tysonite types (0 ⩽ x ⩽ 0.25 and 0.40 ⩽ x ⩽ 0.50 respectively) have been prepared in the PbF 2 – ThF 4 system. The study of the ionic conduction shows that they are good ionic conductors.

Synthese et etude de la conductivite anionique de nouveaux electrolytes MBiF4 (M K, Rb, Tl)

Abstract New anionic electrolytes of formulation MBiF4 (M  K, Rb, Tl) have been prepared. KBiF4, RbBiF4 and the high temperature β-TlBiF4 variety have the fluorite type structure, low-temperature α-TlBiF4 has an ordered α-PbF2 structure. The materials have a conductivity of the same order of magnitude than β-alumina.