Jacques Aubry

Preparation de la solution solide hydrurofluoree CaF2−xHx (0 < x ⩽ 1,24) etude structurale par diffraction des rayons X et par diffraction des neutrons

By studying the CaH2CaF2 system at 700°C, we associate F− and H− anions in the same ternary combination. The existence of solid solutions of composition CaF2−xHx (0 < x ⩽ 1.24) is established, crystallizing in CaF2-type cubic symmetry. The solid solution parameter is considered constant as the composition varies, since there is a variation of 1100 A between pure CaF2 (a = 5.463 A) and the limit phase CaF0.76H1.24 (a = 5.452(5) A). Thus the two anions H− and F− are approximately the same size in the mixed hydride fluorides of calcium. X-ray and neutron diffraction studies indicate a structure in which there is a statistical substitution of fluoride ions by hydride ions on the 8c sites of the CaF2 unit cell.

Preparation and study of ZnxFe0.85−xO (0.085 ≤ x ≤ 0.170)

Abstract In the course of a study of the ZnOFe0.89OFe3O4 system at 900°C, evidence has been obtained for a new phase which can be formulated ZnxFe0.085−xO (0.085 ≤ x ≤ 0.170). The cell is cubic with a parameter a = 12.836 A; the space group determined through electron microdiffraction and X-ray diffraction is Pn3 or Pn3m. This phase is antiferromagnetic with TN varying between 52 and 85°C; it is an n-type semiconductor.

The Li2O-NiO-O2 system at 670C and the consequences of non-stoichiometry on the magnetic properties of the Li x Ni1?x O1y phases

The Li2O-NiO-O2 system is described at 670° C in the oxygen pressure range 1.3×10−8 to 150 bars (and the phase diagram is extended up to Li2NiO3). The consequences of oxygen stoichiometry are emphasized in relation to the magnetic properties.

Préparations et propriétés du diarséniure de beryllium:BeAs2, et du diantimoniure de beryllium:BeSb2

These compounds are obtained through solid-state reaction between the elements in sealed tubes. They remain unaltered with atmospheric moisture. X-ray diffraction gives evidence for pseudocubic symmetry. The atomic stacking is considered to be of disordered sphalerite type. BeAs2 and BeSb2 behave as semiconductors.

Preparation et etude structurale d'un triarseniure de calcium: CaAs3

CaAs 3 is prepared through reaction of gaseous arsenic with calcium metal at 800–900°C in a sealed silica tube. X-ray powder diffraction is indexed by analogy with CaP 3 . The triclinic cell of CaAs 3 is refined by applying the least-squares method: a =5.854(5) ; b =5.832(5) ; c =5.901(5) ; α =70.2(1) o , β =80.3(1) o , γ =75.7(1) o . The compound is isotypic with CaP 3 (space group P ī). Its structure is refined with X-ray powder intensities. The CaAs 3 structure can be interpreted as formed of layers of arsenic, between which we can find the calcium atoms. The chains of As atoms are reminiscent of those existing in the orthorhombic As structure.

Sur l'existence de phases ternaires hydrogenees BeP2−xHy

Abstract The phosphidation of beryllium in the presence of traces of hydrogen leads to non stoichiometric ternary phases BeP2−xHy. The stoichiometric diphosphide BeP2 cannot be obtained. The hydrogenated phases are black and non hygroscopic. The structural study with X rays diffraction, neutrons diffraction, electronic microdiffraction, as well as the crystallographic data from single crystal, provide evidence for a quadratic cell with a = 7,08 A & c = 30,12 A . The stacking is diamond type when considering all the atoms : Be, P and H.