Structures of stable and metastable Ge2Bi2Te5, an intermetallic compound in a GeTe-Bi2Te3 pseudobinary system.
Ge(2)Bi(2)Te(5) in the GeTe-Bi(2)Te(3) pseudobinary system has two single-crystalline phases: a metastable phase with an NaCl-type structure and a stable phase with a nine-layer trigonal structure. In the metastable phase, the structure consists, in the hexagonal notation, of infinitely alternating stacks of Te and Ge/Bi layers at equal intervals along the c axis. On the other hand, in the stable phase those two layers are stacked alternately nine times to form an NaCl block. The blocks are then piled to construct a nine-layered trigonal structure with cubic close-packed stacking. Both ends of each block are covered with Te layers, contrary to the infinite alternation of Ge/Bi and Te layers in the structure of the metastable phase. The Ge/Bi layers in the metastable phase contain as much as 20 at. % vacancies; on the other hand, those in the stable phase are filled with atoms. These two crystalline phases in Ge(2)Bi(2)Te(5) have identical atomic configurations to the two corresponding phases found in Ge(2)Sb(2)Te(5).
Matsunaga
Toshiyuki
T
Characterization Technology Group, Matsushita Technoresearch Inc., 3-1-1 Yagumo-Nakamachi, Moriguchi, Osaka 570-8501, Japan. matsunaga.toshiyuki@jp.panasonic.com
Kojima
Rie
R
Yamada
Noboru
N
Kifune
Kouichi
K
Kubota
Yoshiki
Y
Takata
Masaki
M