Tunable Salt-Inclusion Chalcogenides for Ion Exchange, Photoluminescence, and Scintillation

Salt-inclusion
chalcogenides (SICs) consisting of covalent and
ionic building blocks have emerged as functional materials exhibiting
novel topologies that result from the combination of the chalcogenide-based
frameworks and the salt inclusions contained within them. Nine compositions
of a novel family of SICs [Cs6X]AGa6Q12 (A = Na, K, and Rb; X = F, Cl, and Br; Q = S and Se) were synthesized via halide/polychalcogenide
flux crystal growth and structurally characterized. Ex situ powder X-ray diffraction analysis was used to determine the optimal
synthesis temperatures at which the titled SIC materials crystallized
in the flux. Density functional theory calculations coupled with convex
hull construction were performed to predict the stability of [Cs6X]AGa6Q12 compositions as a function of X, A, and Q and to identify their
decomposition pathways. A combination of single-crystal X-ray diffraction
and energy-dispersive spectroscopy was used to study single-crystal-to-single-crystal
(SC-SC) ion-exchange-reaction, a process that also allowed for the
synthesis of two additional members of this family, [Cs6F]­NaGa6S12 and [Cs6–xRbxBr]­RbGa6S12, which did not form during the direct flux crystal growth. Furthermore,
single crystals of [Cs6X]AGa6Q12:Mn2+ were
obtained through direct flux crystal growth and SC-SC ion-exchange
reactions and studied for their photoluminescent behavior using individual
single crystals. The emission profile changed as a function of Mn2+-content, the A cation identity, and the
synthesis method used. Finally, radioluminescence measurements were
carried out on [Cs6Cl]­NaGa6S12:Mn2+ bulk samples, resulting in bright orange scintillation.