10.1021/acs.inorgchem.7b00002.s001
C. Yang
C.
Yang
B. Y. Qu
B. Y.
Qu
S. S. Pan
S. S.
Pan
L. Zhang
L.
Zhang
R. R. Zhang
R. R.
Zhang
P. Tong
P.
Tong
R. C. Xiao
R. C.
Xiao
J. C. Lin
J. C.
Lin
X. G. Guo
X. G.
Guo
K. Zhang
K.
Zhang
H. Y. Tong
H. Y.
Tong
W. J. Lu
W. J.
Lu
Y. Wu
Y.
Wu
S. Lin
S.
Lin
W. H. Song
W. H.
Song
Y. P. Sun
Y. P.
Sun
Large Positive Thermal Expansion and Small Band Gap
in Double-ReO<sub>3</sub>‑Type Compound NaSbF<sub>6</sub>
American Chemical Society
2017
band gap
NaSbF 6 Double-ReO 3
PTE
type fluorides exhibit
Small Band Gap
NaSbF 6
temperature-dependent X-ray diffractions
F 2 p orbitals
NTE compound CaZrF 6
type structure compound NaSbF 6
phase
2017-04-13 17:23:43
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Large_Positive_Thermal_Expansion_and_Small_Band_Gap_in_Double-ReO_sub_3_sub_Type_Compound_NaSbF_sub_6_sub_/4873598
Double-ReO<sub>3</sub>-type structure compound NaSbF<sub>6</sub> undergoes a low-temperature
rhombohedral to high-temperature cubic phase between 303 and 323 K,
as revealed by temperature-dependent X-ray diffractions. Although
many double-ReO<sub>3</sub>-type fluorides exhibit either low thermal
expansion or negative thermal expansion (NTE), NaSbF<sub>6</sub> exhibits
positive thermal expansion (PTE) with a large volumetric coefficient
of thermal expansion, α<sub>v</sub> = 62 ppm/K, in its cubic
phase. Raman spectroscopy reveals that the low-frequency transverse
vibration of fluorine atoms is stiffened in NaSbF<sub>6</sub>, compared
with the typical NTE compound CaZrF<sub>6</sub> with the same structure.
The related weak contraction associated with the polyhedral rocking
would be overcome by the notable elongation of the Na–F bond
length on heating, thus leading to the large volumetric PTE. Unlike
ScF<sub>3</sub> and CaZrF<sub>6</sub> which are insulators with a
wide band gap, a relative small band gap of 3.76 eV was observed in
NaSbF<sub>6</sub>. The small band gap can be attributed to the hybridization
between the Sb 5s and F 2p orbitals.