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Anisotropic thermal expansion and hydrogen bonding behavior of portlandite: A high-temperature neutron diffraction study
Ist Teil von
Journal of solid state chemistry, 2007-04, Vol.180 (4), p.1519-1525
Ort / Verlag
San Diego, CA: Elsevier Inc
Erscheinungsjahr
2007
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
The structure of deuterated portlandite, Ca(OD)
2, was investigated using time-of-flight neutron diffraction in the temperature range 308–643
K. Rietveld analysis reveals that with increasing temperature, the
c dimension expands at a rate ∼4.5 times larger than that for
a. This anisotropy of thermal expansion is due to rapid increase in the interlayer thickness along
c with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion,
α=
α
0+
α
1
T, where
α
0=5.966×10
−5
K
−1 and
α
1=3.333×10
−8
K
−2. On heating, hydrogen-mediated interatomic interactions within the interlayer become weakened, as reflected by increases in the interlayer D⋯O and D⋯D distances with increasing temperature. Correspondingly, the three equivalent sites over which D is disordered become further apart, suggesting a more delocalized configuration of D at high temperatures.
With increasing temperature, the Ca(OD)
2 structure expands ∼4.5 times larger between the [CaO
6] octahedral layers than within the layers. Correspondingly, the D-mediated interatomic interactions become significantly weakened, and the three equivalent sites over which D is disordered become further apart, suggesting a more delocalized configuration of D at elevated temperatures.