Morphotropy and Temperature-Driven Polymorphism in
A<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> (A = Li, Na, K, Rb, Cs)
Series
Na Yu
Vladislav V. Klepov
Giuseppe Modolo
Dirk Bosbach
Evgeny
V. Suleimanov
Thorsten M. Gesing
Lars Robben
Evgeny V. Alekseev
10.1021/ic5018246.s003
https://acs.figshare.com/articles/dataset/Morphotropy_and_Temperature_Driven_Polymorphism_in_A_sub_2_sub_Th_AsO_sub_4_sub_sub_2_sub_A_Li_Na_K_Rb_Cs_Series/2243683
A new
alkaline thorium arsenate family was obtained and systematically
investigated. The structures of A<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> (A = Li, Na, K, Rb, Cs) were determined from single crystal
X-ray diffraction data. Li<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> and either isostructural K<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> and Rb<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> crystallize in
the monoclinic crystal system. Na<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> and Cs<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> crystallize
in the orthorhombic and tetragonal crystal systems, respectively.
Li<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> consists of [Th(AsO<sub>4</sub>)<sub>2</sub>]<sup>2–</sup> layers with Li atoms in
the interlayer space. The rest of the compounds are based on 3D frameworks.
Differences in local environments of ThO<sub>8</sub> coordination
polyhedra are described in relation to the symmetry. Despite different
local environments of ThO<sub>8</sub> coordination polyhedra and different
structural symmetry, underlying nets of A<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> (A = Na, K, Rb, Cs) were shown to be the same. Single-crystal
and powder Raman spectra were measured, and bands are assigned. DSC
measurements showed phase transitions in K<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> and Rb<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub>,
which were studied using high-temperature powder X-ray diffraction
(HT-PXRD). The data of HT-PXRD demonstrates two high-temperature polymorphic
modification of K<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> and only
one for the isotypic Rb<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub>. The phase transitions in both K and Rb phases are reversible.
2014-10-20 00:00:00
phase transitions
thorium arsenate family
Li 2Th
Rb 2Th
powder Raman spectra
3 D frameworks
DSC
isostructural K 2Th
ThO 8 coordination polyhedra
isotypic Rb 2Th
K 2Th