Robert Lam

Chains, planes, and antimonides

Abstract Ternary rare-earth main-group pnictides RE x M y Pn z where M is a Group 13 or 14 element and Pn is P, As, Sb, or Bi form an emerging class of solid state compounds that frequently display extensive homoatomic Mue5f8M and Pnue5f8Pn bonding in addition to heteroatomic Mue5f8Pn bonding in their anionic substructures. Their structures, properties, and bonding are discussed, with a focus on the antimonides, which have been most heavily investigated.

The metallic Zintl phase Ba3Sn4As6

Abstract The ternary Zintl compound barium tin arsenide, Ba3Sn4As6, has been synthesized at 950xa0°C, and its structure has been determined by single-crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2h5−P21/n with a=8.6374(10)xa0A, b=18.3536(13)xa0A, c=9.7209(11)xa0A, β=90.05(2)°, and Z=4 at 22xa0°C. The structure of Ba3Sn4As6 can be regarded as an intermediate between the hypothetical limiting structures “Ba4Sn2As6”, containing one-dimensional corner-sharing chains of Sn-centered tetrahedra and “Ba2Sn6As6”, containing two-dimensional corrugated layers with pentagonal channels. The Ba2+ cations separate these chains or layers. Resistivity measurements indicate weakly metallic behaviour for Ba3Sn4As6 with a room-temperature resistivity of 2.7×10−4 Ω xa0cm.

Superconductivity in Ba2Sn3Sb6 and SrSn3Sb4

Abstract Resistivity and ac magnetic susceptibility measurements on Ba 2 Sn 3 Sb 6 and SrSn 3 Sb 4 indicate that these Zintl compounds display a transition to a superconducting phase at T C =3.9 K. The Meissner effect was observed for Ba 2 Sn 3 Sb 6 under an applied field of 25 Oe. The signatures for superconductivity, such as high and low velocity conduction electrons and lone pairs, are present for both of these compounds.

Titanium germanium anti­monide, TiGeSb

TiGeSb adopts the PbFCl- or ZrSiS-type structure, with Ti atoms (4mm symmetry) centred within monocapped square antiprisms generated by the stacking of denser square nets of Ge atoms ( m2 symmetry) alternating with less dense square nets of Sb atoms (4mm symmetry).