Synthesis, crystal structure and physical properties of the solid solutions Ca14–x RExCdSb11 (RE = La–Nd, Sm, Gd–Yb, x ≈ 0.85 ± 0.15)

Abstract

This article deals with the new antimonides represented with the general formula Ca14–xRExCdSb11 (RE = La–Nd, Sm, Gd–Yb, x ≈ 0.85 ± 0.15). The 12 studied compounds constitute a nearly complete series of rare-earth metal substituted variants of the ternary Ca14CdSb11 phase. All have been synthesized from the respective elements, employing high-temperature reactions under molten flux conditions. The structures have been fully characterized by single-crystal X-ray diffraction methods. All materials crystallize in the tetragonal Ca14AlSb11 structure type (space group I41/acd, No. 142, Z = 8). Rare-earth element atoms randomly substitute Ca atoms on the four available crystallographic sites, with a noted preference for the Ca2 site in case of the light (La–Nd) rare-earth elements and the Ca1 site in case of the heavier (Sm, Gd–Yb) ones. The electronic structure calculations and resistivity measurements indicate title compounds as degenerated semiconductors. Magnetization measurements at varied temperature show Curie-Weiss paramagnetic behavior consistent with local-moment magnetism due to the 3+ ground state for the rare-earth metal ions. In the case of the Yb-containing sample, a mixed-valence Yb2+/3+ state is apparent. The measured charge transport properties suggest small bandgap degenerate semiconductor-like behavior and suitability for thermoelectrics.

The highly disordered Zintl phase Ca10GdCdSb9 – New example of a p-type semiconductor with remarkable thermoelectric properties

“…The tubes were then taken to the Ar-filled glove box to extract the crystals. The products of these reactions were typically multiphase; in the case of Gd, the mixture of several phases included Ca2CdSb2 18 , Ca14-xGdxCdSb11 (x ≈ 1) 19 and the title phase Ca10GdCdSb9. The crystals obtained from such reaction were only of micron sizes and therefore only suitable for structural elucidation based on single crystal data.…”

New n-Type Zintl Phases for Thermoelectrics: Discovery, Structural Characterization, and Band Engineering of the Compounds A2CdP2 (A = Sr, Ba, Eu)

“…The highly reducing nature of the reaction mixture was shown to, in previous experiments, react at high temperatures with the standard alumna crucibles causing undesirable cracking. 27,28 Single crystals of Eu 2 CdP 2 and Sr 2 CdP 2 were obtained by heating the reactants from 373 K to 1173 K at a rate of 200 K/hr. The peak temperature was held for 24 hrs and then slowly cooled to 823 K at a rate of 3 K/hr.…”

Synthesis, structural characterization, and electronic structure of the novel Zintl phase Ba2ZnP2

“…The highly reducing elemental mixture at elevated temperatures causes unwanted reactions with the alumina, leading to cracked crucibles. Further discussion along these lines can be found elsewhere Baranets et al, 2019b). Ba 2 ZnP 2 was obtained serendipitously as a by-product of the reaction aimed at producing a compound with the formula Ba 3 Zn 2 P 4 .…”