High-pressure phases of Tb2Ni2Sn and Dy2Ni2Sn

Gunter Heymann (1) , Birgit Heying (2) , Ute Ch. Rodewald (2) , Bernard Chevalier (3) , Hubert Huppertz (1) , Rainer Pöttgen (2)

1 Institut für Allgemeine, Anorganische und Theoretische Chemie
2 Institut für Anorganische und Analytische Chemie
3 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The W2B2Co-type ternary stannides Tb2Ni2Sn and Dy2Ni2Sn (space group Immm) show pressure-induced reconstructive phase transitions. Under high-pressure (8 GPa) and high-temperature (1,470 K) treatment they transform to the tetragonal Mo2B2Fe-type high-pressure (HP) modifications: P4/mbm, a = 732.6(1) pm, c = 371.71(9) pm, wR2 = 0.0319, 225 F 2 values for HP-Tb2Ni2Sn and a = 730.3(2) pm, c = 369.1(2) pm, wR2 = 0.0221, 230 F 2 values for HP-Dy2Ni2Sn, with 12 variables per refinement. At 8 GPa HP-Tb2Ni2Sn and HP-Dy2Ni2Sn started to decompose into the equiatomic stannides TbNiSn and DyNiSn and a yet unknown phase. Single-crystal diffractometry revealed the following data: TiNiSi type, Pnma, a = 714.9(1) pm, b = 445.9(1) pm, c = 766.4(1) pm, wR2 = 0.0558, 575 F 2 values, 20 parameters for TbNiSn and a = 710.5(1) pm, b = 445.31(9) pm, c = 765.7(1) pm for DyNiSn. The cell volumes of HP-Tb2Ni2Sn and HP-Dy2Ni2Sn nicely fit into the Iandelli plot of the whole RE2Ni2Sn (RE = rare earth) series of compounds. The polyanionic networks [NiSn] and [Ni2Sn] of the investigated ternary stannides show covalent Ni-Sn bonding with distorted tetrahedral SnNi4/4 coordination (259−279 pm Ni-Sn) in the RENiSn compounds and a square-planar SnNi4/4 arrangement (291−292 pm Ni-Sn) in HP-Tb2Ni2Sn and HP-Dy2Ni2Sn. The nickel atoms form Ni2 pairs with Ni-Ni distances of 250 pm.

Domaines: Matériaux

Gunter Heymann, Birgit Heying, Ute Ch. Rodewald, Bernard Chevalier, Hubert Huppertz, et al.. High-pressure phases of Tb2Ni2Sn and Dy2Ni2Sn. Chemical Monthly = Monatshefte für Chemie, 2014, 145 (6), pp.863-867. ⟨10.1007/s00706-014-1179-8⟩. ⟨hal-00990899⟩