TY - JOUR
T1 - New crystal structure of Nd2Ni7 formed on the basis of stacking of block layers
AU - Iwatake, Yuki
AU - Okamoto, Norihiko L.
AU - Kishida, Kyosuke
AU - Inui, Haruyuki
AU - Ishida, Jun
AU - Kai, Takuya
AU - Yasuoka, Shigekazu
N1 - Funding Information:
This work was supported by JSPS KAKENHI grant numbers 24246113 and 25709066 , and the Elements Strategy Initiative for Structural Materials (ESISM) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, and in part by Advanced Low Carbon Technology Research and Development Program (ALCA) from the Japan Science and Technology Agency (JST).
Publisher Copyright:
© 2015 Hydrogen Energy Publications, LLC.
PY - 2015/2/23
Y1 - 2015/2/23
N2 - The new crystal structure of the intermetallic compound (Nd,Mg)2(Ni,Al)7 has been determined by scanning transmission electron microscopy and electron diffraction. This crystal structure is different from that (either 2H or 3R) usually reported for the intermetallic compound R2T7 (R: rare-earth elements and T: transition-metal elements) in the constitution of block layers. While the block layer for the crystal structure usually reported is of the R2T7 stoichiometric composition consisting of one R2T4 unit layer and two RT5 unit layers, the block layer for the new crystal structure consists of a sub-block layer of the RT3 stoichiometry (formed with one R2T4 unit layer and one RT5 unit layer) and a sub-block layer of the R5T19 stoichiometry (formed with one R2T4 unit layer and three RT5 unit layers), which alternately stack on top of each other. The crystal structure is described based on the order-disorder (OD) theory and the simplest crystal structures (polytypes) among many other polytypes belonging to the same OD family is deduced to be of the 2H-type with the space group of P6¯m2 and of the 6R-type with the space group of R3¯m. The experimentally observed polytype corresponds to the second simplest form of the 6R-type.
AB - The new crystal structure of the intermetallic compound (Nd,Mg)2(Ni,Al)7 has been determined by scanning transmission electron microscopy and electron diffraction. This crystal structure is different from that (either 2H or 3R) usually reported for the intermetallic compound R2T7 (R: rare-earth elements and T: transition-metal elements) in the constitution of block layers. While the block layer for the crystal structure usually reported is of the R2T7 stoichiometric composition consisting of one R2T4 unit layer and two RT5 unit layers, the block layer for the new crystal structure consists of a sub-block layer of the RT3 stoichiometry (formed with one R2T4 unit layer and one RT5 unit layer) and a sub-block layer of the R5T19 stoichiometry (formed with one R2T4 unit layer and three RT5 unit layers), which alternately stack on top of each other. The crystal structure is described based on the order-disorder (OD) theory and the simplest crystal structures (polytypes) among many other polytypes belonging to the same OD family is deduced to be of the 2H-type with the space group of P6¯m2 and of the 6R-type with the space group of R3¯m. The experimentally observed polytype corresponds to the second simplest form of the 6R-type.
KW - Hydrogen storage material
KW - LaNi
KW - Order-disorder (OD) theory
KW - Polytype
KW - Scanning transmission electron microscopy
KW - Superlattice structure
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U2 - 10.1016/j.ijhydene.2015.01.007
DO - 10.1016/j.ijhydene.2015.01.007
M3 - Article
AN - SCOPUS:84922464039
VL - 40
SP - 3023
EP - 3034
JO - International Journal of Hydrogen Energy
JF - International Journal of Hydrogen Energy
SN - 0360-3199
IS - 7
ER -
