Takeo Hattori

Short range structure of B2O3–Cs2O glasses analyzed by x‐ray diffraction and Raman spectroscopy

Structural analyses of pure B2O3, B2O3(90 mol%)–Cs2Ou2009(10 mol%) and B2O3u2009(80 mol%)–Cs2Ou2009(20 mol%) glasses were made by an x‐ray diffraction method and the effects of Cs2O addition were investigated on the short range structure of the glasses. Furthermore, Raman spectroscopic studies were applied to analyze the interatomic interactions between boron and oxygen atoms. Due to x‐ray diffraction, pure B2O3 was confirmed to have BO3 triangles which formed the so‐called boroxol ring structure. When Cs2O was added to B2O3, the boroxol ring structure still remained but some parts of BO3 triangles was definitely converted to BO4 tetrahedra. This result was also supported by Raman spectroscopic observations. The other important consequences were that a Cs atom was surrounded by six O atoms, and four Cs–O interatomic distances were about 3 A but two pairs 3.5 A, indicating that the distorted Cs–O octahedra might exist in the B2O3–Cs2O glasses. This spatial arrangement of Cs and O atoms was quite different from the cor...

Pulsed neutron diffraction study of the short range structure in amorphous arsenic chalcogenides

Abstract The pair distribution functions G ( r )’s of As 2 S 3 and As 2 Se 3 glasses were obtained from the structure factors S ( Q )’s. The structural parameters were refined by applying the correlation method in the ( Q , Q·i ( Q )) space. Although the structural parameters by PND were somewhat different from those by XRD, the peak shape in PND was clearer than in XRD. The local structure of the glasses was similar to that of orpiment (As 2 S 3 crystal) with AsS 3 pyramids. However, the nearest neighbor distances of As–S pair were 2.29xa0A in PND, 2.27xa0A in XRD, and 2.25xa0A (average value of As–S bonds in crystal), implying the little expansion of AsS 3 -type pyramids and the variation in linkage of pyramids.

Short range structure of B2O3–Rb2O glasses by neutron diffraction

Abstract The short range structure of (1− x )B 2 O 3 – x Rb 2 O ( x =0.05–0.30) glasses was investigated to study by time-of-flight neutron scattering experiments using the high intensity total scattering spectrometer (HIT). In each correlation function of G ( r ) curve, the first peak appeared at around r =1.4xa0A which was thought to be due to the B–O correlation in boroxol ring composed of trigonal planer BO 3 units and tetrahedral BO 4 units. The results in the short range structure of borate glasses were similar to those which were calculated by two molecular orbital methods.

Pulsed neutron diffraction study on the short range structure of B2O3-Ag2O glasses

Abstract The short range structure of (1− x )B 2 O 3 – x Ag 2 O ( x =0.05–0.30) glasses was investigated by time-of-flight neutron scattering experiments. Radial distribution analyses were applied to extract the structural information, but the structural parameters for each atomic pair were finally optimized in the Q -space. The bond distances of near neighbor B–O pairs were estimated at 0.138 and 0.145 nm, and the corresponding coordination numbers were 3 and 4, respectively. These were ascribed to the B–O correlations in distorted six-membered rings consisting of planer trigonal units and tetrahedral ones. The silver atoms serve to hold the networks together through coordination with oxygen atoms, thereby the nearly octahedral arrangements of oxygen atoms around a silver atom were found to exist in these glasses. The octahedral units were distorted to such an extent that the Ag–O distances were ranging from 0.25 to 0.32 nm. The existence of medium range order was also confirmed in the structure factor S ( Q ) over the composition range of this work.

Characterization of perovskite-type GdFeO3 powders prepared by amorphous citrate process

The purposes of this study were to obtain GdFeO 3 powders by calcining their precursor gels which were prepared from Gd 2 O 3 and Fe 2 O 3 by the amorphous citrate process, and to characterize the powders in comparison with those prepared by the solid-state reaction (SSR) of Gd 2 O 3 and Fe 2 O 3 powders. Furthermore, it was attempted to estimate precisely crystallite sizes and lattice constants of GdFeO 3 powders by x-ray diffraction line profile analyses

X-ray diffraction study on the short-range structure of K2O–TeO2 glasses and melts

Abstract The short-range structure of K 2 O–9TeO 2 and K 2 O–4TeO 2 in amorphous states such as glass and melt has been investigated by X-ray diffraction (XRD) and semi-empirical molecular orbital calculation (AM1-MOPAC method). The structure of amorphous alkali tellurites consisted of the TeO 4 trigonal bipyramids (tbp) and the TeO 3 trigonal pyramids (tp). Confirmed in the present work is that the TeO 4 trigonal bipyramids characteristics of TeO 2 -based glasses transform into TeO 3 trigonal pyramids with increasing modifier K 2 O content and a rise of temperature. The usage of XRD and MOPAC enabled us to comprehend in some details what to happen in phase transition from glasses to melts.

X-ray diffraction study of the short-range structure of LiCl–Li2O–TeO2 glasses

Abstract Structural analyses of amorphous LiCl–Li 2 O–TeO 2 were made by X-ray diffraction. The basic structure of the tellurite glasses consisted of the TeO 4 trigonal bipyramids and the TeO 3 trigonal pyramids. The resulting structure was in agreement with that so far analyzed by infrared spectroscopy. The effects of LiCl addition on the short-range structure were also discussed according to the mutual use of the radial distribution analysis and the correlation method in this work.

Neutron diffraction study on network structure of As2Se3–Ag2Se glasses and selenium coordination around silver atom

Abstract The short range structure analysis of (1− x )As 2 Se 3 – x Ag 2 Se ( x =0.05–0.30) glasses were studied by the time-of-flight (TOF) neutron diffraction method, and the effects of Ag 2 Se addition on the network structure of AsSe 3 trigonal pyramid were investigated. The As–Se and Se–Se distances of the AsSe 3 trigonal pyramids in As 2 Se 3 –Ag 2 Se glasses were at 2.45–2.54 and 3.72–3.86xa0A, respectively, and thus the bond angles of ∠Se–As–Se for the AsSe 3 trigonal pyramids in these glasses were calculated to be about 99.0°. These results indicate the existence of AsSe 3 trigonal pyramid structure in these glasses, but the shape was not as symmetrical as in crystalline As 2 Se 3 .

Thermal behaviour and HIP treatment of lead telluride

Analyse de la decomposition thermique de PbTe dans lair. Influence de la temperature, de la pression et du temps de trempe lors de la pression isostatique a chaud sur la densification de PbTe. Etude de la microstrucure par microscopie electronique a balayage

Short-range structure of a multicomponent glass by an X-ray diffraction method

Letude porte sur le systeme 71,67 SiO 2 -12,76 Na 2 O-8,01 CaO-6,01 MgO (% mol) combinant aussi Al 2 O 3 , K 2 O, Fe 2 O 3 et TiO 2