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Titolo:
NEUTRON-SCATTERING INVESTIGATION OF HYDROGENIC SPECIES IN THE AMMONIUM MOLYBDENUM BRONZE (NH4)0.24H0.03MOO3
Autore:
SLADE RCT; PRESSMAN HA;
Indirizzi:
UNIV EXETER,DEPT CHEM,STOCKER RD EXETER EX4 4RJ DEVON ENGLAND
Titolo Testata:
Journal of materials chemistry
fascicolo: 4, volume: 4, anno: 1994,
pagine: 501 - 508
SICI:
0959-9428(1994)4:4<501:NIOHSI>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
TUNGSTEN TRIOXIDE FRAMEWORK; TOPOTACTIC REDOX REACTIONS; ION REORIENTATIONS; INELASTIC NEUTRON; COMPOUND; MOTIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
27
Recensione:
Indirizzi per estratti:
Citazione:
R.C.T. Slade e H.A. Pressman, "NEUTRON-SCATTERING INVESTIGATION OF HYDROGENIC SPECIES IN THE AMMONIUM MOLYBDENUM BRONZE (NH4)0.24H0.03MOO3", Journal of materials chemistry, 4(4), 1994, pp. 501-508

Abstract

Incoherent inelastic neutron scattering (IINS) and quasielastic neutron scattering (QENS) have been used in investigation of the ammonium bronze (NH4)0.24H0.003MoO3. The IINS vibrational spectrum reveals the presence of NH4+ (in the interlayer region of the alpha-MoO3 host) and hydroxy groups (in intralayer bridging positions as in the parent hydrogen bronze, H0.27MoO3). Variable-temperature QENS measurements on instruments of differing elastic energy resolutions and differing ranges of elastic scattering vector magnitude have been used in investigationof motions of the NH4+ ion. Broadenings are observed in QENS spectra over a remarkably large temperature range. In analysis of all spectra it was necessary to invoke a variable 'static fraction' of hydrogen, this arising from the temperature-dependent defect structures associated with incomplete filling of NH4+ sites and consequent variations in local environment of NH4+ ions. Variations in the scattering law [S(Q,omega)] at low temperature were consistent with reorientation of order > 3 of a fraction of the NH4+ present and were fitted assuming a four-fold barrier. At higher temperatures, spectra were treated using the isotropic rotational diffusion model for those reorienting ions giving discernible quasielastic broadenings, this diffusion being consequent on interaction of rotations of low-energy barrier with lattice modes.

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Documento generato il 21/09/20 alle ore 06:11:30