Die Kristallstruktur von Ca₂Sn und Ca₂Pb

Abstract

Röntgenographische Untersuchungen an Einkristallen der Verbindungen Ca2Sn und Ca2Pb ergaben, daß diese isotyp mit Ca2Si und Ca2Ge im Strukturtyp des PbCl2 (C‐23 Typ) Kristallisieren. Die Gitterkonstanten betragen: Ca2Sn: a = 9,562 ± 0,004; b = 7,975 ± 0,004; c = 5,044 ± 0,003 Å. Ca2Pb: a = 9,647 ± 0,004; b = 8,072 ± 0,004; c = 5,100 ± 0,003 Å. Die wahrscheinliche Raumgruppe ist D 2h16‐Pbnm; die Atome besetzen die Punktlage Die gefundenen Parameter sind außer den y‐Werten der Schwermetallatome bei beiden Verbindungen gleich und betragen: xSn = xPb = 0,111; xCa1 = 0,067; xCa2 = 0,683. ySn = 0,253, yPb = 0,250; yCa1 = 0,655; yCa2 = 0,513. Die Verbindungen Ca2Si, Ca2Ge, Ca2Sn und Ca2Pb werden mit den entsprechenden Magnesiumverbindungen verglichen. Beide Verbindungsgruppen haben ähnlichen Bindungstyp; Abstandsbetrachtungen zeigen, daß es sich um kovalente Bindung handelt.

Thermoelectric Properties of Ca2Sn/Ca3SnO

“…Estimated lattice parameters of Ca 2 Sn and Ca 3 SnO, are collected in Table I. It is worth nothing that the previous experimental reports [1][2][3] shows very different values of lattice parameters (parameter a varies in different reports from 7.5 Å to 12.15 Å). During the 24 hour XRD measurement the concentration of Ca 2 Sn phase diminished and the concentration of Ca 3 SnO phase increased despite Fig.…”

“…Thermoelectric properties were measured using Thermal Transport Option (TTO) for Quantum Design PPMS system. Several previous attempts [1][2][3] has shown that these samples turn into powder after contact with air withing few minutes. As we do not have the possibility to transfer the sample to PPMS platform without contact with air (note that in order to perform thermoelectric measurements, the sample must have the correct shape) after melting we covered the sample with mineral oil, polished to correct shape, than cleaned oil residues and installed within TTO option.…”

“…This type of materials was first synthesized in 1961 (Eckerlin), and its structure was determined by XRD measurements [1]. There are little experimental studies of thermodynamic and electrical properties of these compounds [2][3][4], as even in the first paper it was observed that these materials within a very short time turn into black powder after exposure to air.…”

Investigation of structural, elastic, and lattice-dynamical properties of Ca2Si, Ca2Ge, and Ca2Sn based on first-principles density functional theory

“…1 shows the unit cell of Ca 2 X (X = Si, Ge, and Sn) with the orthorhombic Pnma structure. There are two crystallographically inequivalent 4c sites for Ca (Ca I and Ca II ) and a single 4c site for X in Ca 2 X [16,17]. There are four formula units distributed over the four Ca I , four Ca II , and four X sites per unit cell.…”

Neue gemischte Zinn-reiche Erdalkalimetall-Stannide – Synthese, Strukturchemie und chemische Bindung / New Mixed Tin-rich Alkaline Earth Stannides – Synthesis, Structural Chemistry and Chemical Bonding

“…Im Unterschied zu den klassischen Zintl-Phasen [3,4] wie z. B. KSn [5,6], Ca 2 Sn [7], CaSn [8,9] oder BaSn 2 [10] bzw. Clusterverbindungen [11] wie z.…”