Marie-France Mercier

Etude in situ par spectrométrie vibrationnelle de couches minces electrochromes d'oxyde de tungstène WO3 et d'oxyde de molybdene MoO3

Raman spectroscopy, internal and specular I.R. reflection spectroscopies have been applied to WO3 and MoO3 thin films (∼ 5,000 A). These films are amorphous and transform to crystalline materials at 400°C. Structural similarities between WO3 films and the new hexagonal form of WO3 may explain the electrochromic properties of the former.

Coumarins from the aerial parts of Chorilaena quercifolia

Abstract The aerial parts of Chorilaena quercifolia have yielded one alkaloid, skimmianine, two common coumarins, 5,7,8-trimethoxycoumarin and marmesin, and two novel coumarins whose structures were established on the basis of spectral data, as 7-(3,7-dimethyl-5-oxooct-6-enyloxy)coumarin and 8,9-dihydro-8(1-hydroxy-1-methylethyl)-8-(3-methylbut-2-enyloxy)furo-{2,3- h }-benzopyran-2-one.

Correlations between structure and conductivity in NaPO3-TiO2 glasses

Abstract (NaPO 3 ) (1- x ) -(TiO 2 ) x glasses ( x ≤0.4) were prepared by melting at 1400°C mixtures of NaPO 3 and TiO 2 . The melt was poured out in a graphite mold and annealed. DSC measurements give the variation of T g from 290°C (NaPO 3 ) to 620°C ( x =0.4). FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO 3 ) ∞ chains for NaPO 3 to PO 4 groups in the richest TiO 2 glass. Ionic conductivity is obtained by impedance plots (10 −2 -10 5 Hz) on cylindrical cells. It decreases from 10 −4 to 7×10 −6 ω −1 cm −1 at 200°C; the activation energy increases from 13.5 to 14 Kcal/mole. Neutron scattering (λ=0.9 A; Q:0.3 to 14 A −1 ) leads to pair distribution RDF with peaks at 1.5 (P-O) and 2.4 A (O-O and Na-O). ΔRDF enables discrimination between pairs either including Ti or not. The first negative peak at 1.95 A is assigned to the hexacoordination (Ti-O) of titanium. TiO 2 addition does not increase the conductivity, because the Na + molar fraction decreases and its environment is unmodified.