New type-I clathrates with ordered Eu distribution

Strongly correlated cage compounds for thermoelectric applications?

“…K6Eu2Zn5Ge4j and K6Eu2Cd5Ge4l have been investigated but no evidence for effects of increased hybridization could be found. The electrical resistivity of K6Eu2Cd5Ge4l is not metal-like as in Q-Eu8Gal6-xGe3o+x but semiconductor-like, in agreement with the lower charge carrier concentration estimated above for the K-containing clathrates [15]. Thermal transport measurements are still due.…”

“…While this may be due to the onset of Kondo screening the 4f-conduction electron interaction is still much too weak to promote a strongly correlated state. From a calculation of the RKKY coupling as a function of the charge carrier concentration we could conclude that the carrier concentration is below 4 x 1026 m-3, i.e., smaller than the lowest concentration reached for Q-Eu8Gal6-xGe3o+x [15].…”

“…In order to destabilize its divalent state, Eu was replaced by monovalent K in the larger, tetrakaidekahedral cages [15]. The resulting compound K6Eu2GajOGe36 orders ferromagnetically at a much reduced temperature of only 3.8 K. Low-temperature magnetization measurements are suggestive of slightly reduced magnetic moments of Eu.…”

Cu and Zn Substituted Silicon Clathrates with the Cubic Type‐II Structure: Synthesis and Characterization of Cs8Na16Cu3.8Si132.2 and Cs8Na16Zn6.9Si129.1

“…This disparity is likely due to the aforementioned challenges synthesizing selectively type-II clathrates. As discussed in earlier publications, [12,19] 5 Ge 41 , [23] and, alongside many other type-I clathrates with complete occupation of all cages by one kind of guest atoms. [12,19] The downside of this approach is that in multinary systems, there are many competing binary and ternary phases, and as result, the synthetic difficulties are greatly exacerbated.…”

Investigation of substitution effects and the phase transition in type-I clathrates Rb Cs8–Sn44□2 (1.3≤x≤2.1) using single-crystal X-ray diffraction, Raman spectroscopy, heat capacity and electrical resistivity measurements

“…Some other cases of type-I clathrates with two different kinds of encaged atoms have been so far structurally characterized: (a) the compound K 1.6 Cs 6.4 Sn 44 [1] that also exhibits mixed occupancy in both cationic positions (b) solid solutions of polycationic [Sn 24 P 19.3 ]Br x I 8-x (0rxr8) and [Sn 24 P 19.3 ]Cl y I 8-y (yr0.8) [12] (c) Na 2 Ba 6 Si 46 with pdod and tkad fully occupied by Na and Ba, respectively [13] and (d) Eu 2 K 6 Ga 10 Ge 36 [14] also with fully ordered cations. The rattling of the encaged cations is regarded as a significant (in)stability factor and therefore the well fitting Cs radius in the relatively large framework cavities of the Sn atoms justifies the trend towards type-I clathrate formation.…”