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I. Zeiringer, A. Grytsiv, E. Bauer, G. Giester, P. Rogl:
"Phase Relations and Crystal Structures in the Ternary Systems Sr-{Ag, Au}-{Si, Ge}";
Zeitschrift für Anorganische und Allgemeine Chemie, 641 (2015), S. 1404 - 1421.

Phase equilibria in the isothermal sections of the ternary systems Sr-{Ag, Au}-{Si, Ge} were determined in the (Si) or (Ge) rich part up to 33.3 at % Sr after annealing at 700 °C (Sr-{Ag, Au}-Ge) or 800 °C (Sr-{Ag, Au}-Si). Tentative liquidus projections were constructed for the Si, Ge-rich part of all the four phase diagrams. These systems are characterized by a series of ternary compounds, exhibiting in some cases extended homogeneity regions at a constant Sr content. Compounds in the Si, Ge-rich region essentially form along two sections: at 33.3 at % Sr (AlB2-family) and at 20 at % Sr (BaAl4-family of structure types). The crystal structures of the novel equilibrium phases were derived by X-ray single crystal diffraction: Sr2Ag1+xSi3-x-y□y [Sr2LiSi3 type; x = 0.17, y = 0.43: a = 8.4488(2), b = 14.6376(2), c = 18.4018(2) Å], SrAg2-xSi2+x [ThCr2Si2 type; x = 0.1: a = 4.37664(6), c = 10.4517(2) Å], Sr(Au1-y□y)(Si1-xAux)3 [BaNiSn3 type; x = 0.59, y = 0.64: a = 4.4594(2), c = 10.1013(6) Å] and SrAu5-x□xSi2 [BaAu5Si2 type; x = 0.7: a = 8.7557(3), b = 6.9945(2), c = 9.8873(3) Å]. The crystal structures of Sr(AgxGe1-x)2 [AlB2 type; x = 0.25: a = 4.3431(2), c = 4.5938(1) Å], SrAg2-xGe2+x [ThCr2Si2 type; x = 0.2: a = 4.4476(2), c = 10.822(1) Å] and Sr(AuxGe1-x)2 [AlB2 type; x = 0.25: a = 4.3263(2), c = 4.5852(7) Å] were evaluated by X-ray powder Rietveld analysis. Composition dependent polymorphism was observed among the BaAl4-type derivative structures for SrAu2-xGe2+x: CaBe2Ge2 type [x = 0.45: a = 4.4796(2), c = 10.6315(5) Å], BaCu2Sb2 type [x = 0.35: a = 4.4866(2), c = 31.808(1) Å] and ThCr2Si2 type [x = 0.2: a = 4.5214(4), c = 10.336(1) Å]. Similarly, Sr(AuxSi1-x)2 exhibits the Ca2AgSi3 structure type [x = 0.25: a = 8.3407(2), b = 14.4465(2) and c = 9.2664(3) Å] and the AlB2 type [x = 0.375: a = 4.2241(2), c = 4.5799(3) Å]. The structural chemistry of the BaAl4 derivative structures within the sections SrT2-xX2+x is discussed.

http://dx.doi.org/10.1002/zaac.201500045