title: The first silicon-based cationic clathrate III with high thermal stability: Si172-xPxTey (x=2y, y>20).
abstract: A new representative of a very rare clathrate III family, Si130P42Te21, has been synthesized from the elements. It crystallizes in the tetragonal space group P4(2)/mnm (no. 136) with the unit cell parameters a=19.2632(3) angstroms, c=10.0706(2) angstroms. Single crystal X-ray diffraction and solid state 31P NMR revealed a non-random distribution of phosphorus atoms over the framework positions. The crystal structure features a peculiar packing of large polyhedra Te@(Si/P)(n) never observed before for cationic clathrates. Despite the structural complexity, the composition of the novel clathrate Is in accordance with the Zintl rule, which was confirmed by a combination of optical metallography, scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDXS), as well as by diamagnetic and semiconducting behavior of the synthesized phase. Clathrate Si130P42Te21 exhibits the highest reported thermal stability for this class of materials, it decomposes at 1510 K. This opens new perspectives for the creation of clathrate-based materials for high-temperature applications.
authors.affiliation: Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strabe 40, 01187 Dresden, Germany.
authors.forename: Julia V
authors.initials: JV
authors.lastname: Zaikina
authors.forename: Kirill A
authors.initials: KA
authors.lastname: Kovnir
authors.forename: Frank
authors.initials: F
authors.lastname: Haarmann
authors.forename: Walter
authors.initials: W
authors.lastname: Schnelle
authors.forename: Ulrich
authors.initials: U
authors.lastname: Burkhardt
authors.forename: Horst
authors.initials: H
authors.lastname: Borrmann
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schwarz
authors.forename: Yuri
authors.initials: Y
authors.lastname: Grin
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Shevelkov