An exploration of the crystal chemistry of exciting luminescent title compounds – possible phosphors – is discussed also employing magnetic measurements.

The intermetallic compounds RET3X2 (RE = La–Nd, Sm, Gd, Tb; T = Pd, Pt; X = In, Sn) have been synthesized from the elements by arc-melting and subsequent annealing sequences in tube or induction furnaces. The samples were characterized through Guinier powder diffraction patterns, and several structures were refined from single crystal X-ray diffractometer data. These indium and tin intermetallics crystallize with the orthorhombic CePd3In2-type structure, space group Pnma. The palladium (platinum) and indium (tin) atoms in the RET3X2 structures build up complex three-dimensional [T3X2]δ− polyanionic networks in which the rare earth atoms fill cavities. The striking structural motifs concern the indium, respectively tin substructures, in which part of the indium and tin atoms have distorted square planar homoatomic coordination environments: In1In12In22 units in PrPd3In2 with interatomic distances 325 pm In1–In1 and 332 pm In1–In2 as well as Sn1Sn12Sn22 units in PrPt3Sn2 with the larger distances of 356 pm for Sn1–Sn1 and of 344 pm for Sn1–Sn2. Temperature dependent magnetic susceptibility measurements have indicated Pauli paramagnetism or diamagnetism for the lanthanum compounds, van-Vleck paramagnetism for SmPt3In2 and Curie-Weiss paramagnetism for the remaining compounds. Antiferromagnetic ordering was detected at TN = 4.0(1) K for CePt3In2 and at TN = 3.5(1) K for SmPt3In2. CePt3In2 shows a metamagnetic transition at an external magnetic field of 47(3) kOe.

EuAuIn and SrAuIn (TiNiSi type structure, space group Pnma) form a complete solid solution Eu1–xSrxAuIn. Samples with x = 0.2, 0.4, 0.5, 0.6 and 0.8 were prepared by melting of the elements in sealed tantalum ampoules followed by slow cooling. The samples were characterized through Guinier powder patterns. The X‐ray data confirm Vegard type behavior. The crystal structures of Eu0.8Sr0.2AuIn and Eu0.5Sr0.5Au1.02In0.98 were refined from single‐crystal X‐ray diffraction data in order to confirm the Eu/Sr site occupancies. Temperature‐dependent magnetic susceptibility data confirm divalent europium. The Néel temperature linearly drops from 21.0 K for EuAuIn and long‐range magnetic ordering is still present in the x = 0.8 sample with TN = 4.1 K. Low‐field measurements indicate two successive magnetic ordering temperatures for all samples, resulting from a complex interplay of antiferromagnetic and ferromagnetic interactions, similar to the tetrelides EuMgX (X = Si, Ge, Sn). 151Eu Mössbauer spectra confirm the divalent ground state and show complex magnetic hyperfine field splitting at 6 K.

The crystal structure of diamagnetic borate chloride Sn2B5O9Cl exhibits two crystallographically independent tin sites which both show pronounced lone-pair activity of the tin atoms. This is reflected in substantial quadrupole splitting in the 119Sn Mössbauer spectrum. The isomer shifts of 3.887(8) and 4.137(7) mm s−1 clearly indicate divalent tin. In agreement with bond valence calculations, the Sn1 atoms have a lower charge and the higher isomer shift, compatible with a higher electron density at the tin nuclei.

Samples of the solid solution Eu1–xSrxAu4Cd2 (YbAl4Mo2 type, space group I4/mmm) with x = 0.2, 0.4, 0.6, and 0.8 were synthesized from the elements by annealing in sealed tantalum ampoules. The structures of Eu0.66Sr0.34Au4.12Cd1.88 and Eu0.22Sr0.78Au4.10Cd1.90 were refined from X-ray single crystal diffractometer data. Besides the expected Eu/Sr mixing on the 2a sites the diffraction data revealed also a small degree of Cd/Au mixing on the 4d sites of the cadmium chains. Temperature dependent magnetic susceptibility data show divalent europium and ferromagnetic ground states for all samples and a linear decrease of the Curie temperature from 16.3 K for EuAu4Cd2 to 2.9 K for Eu0.2Sr0.8Au4Cd2. Magnetization isotherms characterize the Eu1 − xSrxAu4Cd2 samples as soft ferromagnets. The divalent nature of europium is underpinned by 151Eu Mössbauer spectra. The decreasing Curie temperature goes along with a decreasing magnetic hyperfine field at 6 K. Graphic abstract