TY - JOUR
T1 - Structure and composition analysis of the phases in the system Th-Pd-B-C containing superconductors with Tc = 14.5 K and Tc = 21 K
AU - Zandbergen, H. W.
AU - Gortenmulder, T. J.
AU - Sarrac, J. L.
AU - Harrison, J. C.
AU - de Andrade, M. C.
AU - Hermann, J.
AU - Han, S. H.
AU - Fisk, Z.
AU - Maple, M. B.
AU - Cava, R. J.
N1 - Funding Information:
Two of the authors (HWZ and TJG) wish to thank the Foundation for Fundamental Research on Matter and the Netherlands Technology Foundation for support. Work at UCSD was supported in part by the U.S. Department of Energy under Grant No. DE-FC03-86ER45230. Financial support of the CNPq of Brasil (MCA) and of the German Academic Exchange Service (JH) is gratefully acknowledged.
PY - 1994/11/1
Y1 - 1994/11/1
N2 - Several specimens in the system Th-Pd-B-C with nominal compositions ThPd3B2C and ThPd3B3C (as melted and annealed), containing superconducting phases exhibiting Tc's of 14.5 K and 21 K, have been studied with EPMA, electron diffraction, EDX element analysis and HREM. A number of phases (approximate compositions are given) have been observed: (1) ThPd2B2C, I-centered tetragonal, a = 0.375, c = 1.07 nm, which can be related to the Tc of 14.5 K; (2) ThPd0.65B4.7, P-type cubic, a = 0.42 nm, with short-range ordered superstructure resulting in diffuse streaks in the electron-diffraction pattern; this phase is suggested to be the 21 K superconducting phase; (3) ThPd3 P-type hexagonal, a = 0.58, c = 0.98 nm; (4) ThPd8B3, I-centred orthorhombic a = 0.84, b = 0.90, c = 1.67 nm; (5) ThPd3B2C, with unknown structure; (6) ThB4, tetragonal a = 0.72, c = 0.41 nm; (7) graphitic C. Annealing of the specimen ThPd3B2C at 1050°C results in the disappearance of ThPd2B2C and the loss of the Tc at 14.5 K but a strong increase of the 21 K superconducting fraction with a corresponding strong increase of the phases ThPd0.65B4.7 and ThPd3. HREM indicates that ThPd0.65B4.7 adopts a modified CaB6 structure in which the cube face, 1 2, 1 2, 0, which is vacant in CaB6, is partially occupied by Pd with the removal of some B atoms. The superstructure indicates a short-range ordering (clustering) of the Pd atoms.
AB - Several specimens in the system Th-Pd-B-C with nominal compositions ThPd3B2C and ThPd3B3C (as melted and annealed), containing superconducting phases exhibiting Tc's of 14.5 K and 21 K, have been studied with EPMA, electron diffraction, EDX element analysis and HREM. A number of phases (approximate compositions are given) have been observed: (1) ThPd2B2C, I-centered tetragonal, a = 0.375, c = 1.07 nm, which can be related to the Tc of 14.5 K; (2) ThPd0.65B4.7, P-type cubic, a = 0.42 nm, with short-range ordered superstructure resulting in diffuse streaks in the electron-diffraction pattern; this phase is suggested to be the 21 K superconducting phase; (3) ThPd3 P-type hexagonal, a = 0.58, c = 0.98 nm; (4) ThPd8B3, I-centred orthorhombic a = 0.84, b = 0.90, c = 1.67 nm; (5) ThPd3B2C, with unknown structure; (6) ThB4, tetragonal a = 0.72, c = 0.41 nm; (7) graphitic C. Annealing of the specimen ThPd3B2C at 1050°C results in the disappearance of ThPd2B2C and the loss of the Tc at 14.5 K but a strong increase of the 21 K superconducting fraction with a corresponding strong increase of the phases ThPd0.65B4.7 and ThPd3. HREM indicates that ThPd0.65B4.7 adopts a modified CaB6 structure in which the cube face, 1 2, 1 2, 0, which is vacant in CaB6, is partially occupied by Pd with the removal of some B atoms. The superstructure indicates a short-range ordering (clustering) of the Pd atoms.
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U2 - 10.1016/0921-4534(94)90791-9
DO - 10.1016/0921-4534(94)90791-9
M3 - Article
AN - SCOPUS:0028539663
SN - 0921-4534
VL - 232
SP - 328
EP - 336
JO - Physica C: Superconductivity and its applications
JF - Physica C: Superconductivity and its applications
IS - 3-4
ER -