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Mechanistic insight of KBiQ (Q = S, Se) using panoramic synthesis towards synthesis-by-design
Ist Teil von
Chemical science (Cambridge), 2021-02, Vol.12 (4), p.1378-1391
Erscheinungsjahr
2021
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
Solid-state synthesis has historically focused on reactants and end products; however, knowledge of reaction pathways, intermediate phases and their formation may provide mechanistic insight of solid-state reactions. With an increased understanding of reaction progressions, design principles can be deduced, affording more predictive power in materials synthesis. In pursuit of this goal,
in situ
powder X-ray diffraction is employed to observe crystalline phase evolution over the course of the reaction, thereby constructing a "panoramic" view of the reaction from beginning to end. We conducted
in situ
diffraction studies in the K-Bi-Q (Q = S, Se) system to understand the formation of phases occurring in this system in the course of their reactions. Powder mixtures of K
2
Q to Bi
2
Q
3
in 1 : 1 and 1.5 : 1 ratios were heated to 800 °C or 650 °C, while simultaneously collecting diffraction data. Three new phases, K
3
BiS
3
, β-KBiS
2
, and β-KBiSe
2
, were discovered. Panoramic synthesis showed that K
3
BiQ
3
serves an important mechanistic role as a structural intermediate in both chalcogen systems (Q = S, Se) in the path to form the KBiQ
2
structure. Thermal analysis and calculations at the density functional theory (DFT) level show that the cation-ordered β-KBiQ
2
polymorphs are the thermodynamically stable phase in this compositional space, while Pair Distribution Function (PDF) analysis shows that all α-KBiQ
2
structures have local disorder due to stereochemically active lone pair expression of the bismuth atoms. The formation of the β-KBiQ
2
structures, both of which crystallize in the α-NaFeO
2
structure type, show a boundary where the structure can be disordered or ordered with regards to the alkali metal and bismuth. A cation radius tolerance for six-coordinate cation site sharing of
∼ 1.3 is proposed. The mechanistic insight the panoramic synthesis technique provides in the K-Bi-Q system is progress towards the overarching goal of synthesis-by-design.
This work uses
in situ
powder X-ray diffraction studies to observe crystalline phase evolution over the course of multiple K-Bi-Q (Q = S, Se) reactions, thereby constructing a "panoramic" view of each reaction from beginning to end.
Sprache
–
Identifikatoren
ISSN: 2041-6520
eISSN: 2041-6539
DOI: 10.1039/d0sc04562d
Titel-ID: cdi_rsc_primary_d0sc04562d
Format
–
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