Structural phase transitions in molecular graphite intercalation compounds

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5678357

Homma, H

The Molecular Graphite Intercalation Compounds (GIC's) SbCl/sub 5/, HNO/sub 3/, and MoCl/sub 5/ GIC's, in particular SbCl/sub 5/ GIC, have been investigated in great detail for the first time in terms of their structural properties using diffuse x-ray scattering techniques. Higher stages (n greater than or equal to 3) of SbCl/sub 5/ GIC were found to be quasi two-dimensional in terms of the structural behavior of the intercalant layers. Two segregated phases were found in this system, a ..sqrt..7 x ..sqrt..7 superlattice consisting of SbCl/sub 6//sup -/ molecules and a further phase consisting of SbCl/sub 3/ molecules which is fluid-like at ambient temperatures. The former structure showed commensurate-incommensurate (C-I) and melting transitions at T approx. = 375K and 455K respectively. The commensurability ..sqrt..7 is close to the Coppersmith limit ..sqrt..8 below which the structure is destabilized by dislocations. It was pointed out that this incommensurate phase could alternately be a fluid with unusually long-range correlations. An order-disorder transition in the SbCl/sub 3/ molecular phase was observed and documented. The low temperature phase (T/sub 1/ approx. = 220K) is identified by an incommensurate ..sqrt..39 x ..sqrt..39 superlattice and the high temperature (T > T/sub 1/) disordered phase is fluid-like for stage n greater than or equal to 2. The I-..sqrt..39 x ..sqrt..39 phase is interpreted as arising from the formation of dimerized SbCl/sub 3/ molecules below T/sub 1/ with oppositely paired dipole moments. The commensurate-..sqrt..39 x ..sqrt..39 structure was observed at ambient temperature in stage 1 samples.

• OSTI ID: 5678357
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ANTIMONY CHLORIDES
ANTIMONY COMPOUNDS
CARBON
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
CLATHRATES
COHERENT SCATTERING
DIFFRACTION
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
MINERALS
MOLYBDENUM CHLORIDES
MOLYBDENUM COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
REFRACTORY METAL COMPOUNDS
SCATTERING
SUPERLATTICES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION