TY - JOUR
T1 - Synthesis, boron-nonstoichiometry and hardness of perovskite-type rare earth rhodium borides RRh3Bx (R = La, Gd, Lu and Sc)
AU - Shishido, T.
AU - Ye, J.
AU - Okada, S.
AU - Kudou, K.
AU - Iizumi, K.
AU - Oku, M.
AU - Ishizawa, Y.
AU - Sahara, R.
AU - Kumar, V.
AU - Yoshikawa, A.
AU - Tanaka, M.
AU - Horiuchi, H.
AU - Nomura, A.
AU - Sugawara, T.
AU - Obara, K.
AU - Amano, T.
AU - Kohiki, S.
AU - Kawazoe, Yoshiyuki
AU - Nakajima, K.
N1 - Funding Information:
This study was performed under the Interuniversity Cooperative Research Program of the Laboratory for Advanced Materials (LAM), Institute for Materials Reseach (IMR), Tohoku University. V.K. thankfully acknowledges hospitality at IMR, Tohoku University. We are grateful to the staff of the Center for Computational Material Science of IMR, Tohoku University for allowing the use of the Hitachi RS-8000/64 super computing facility and their kind support.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2006/2/9
Y1 - 2006/2/9
N2 - Rare earth ternary borides, RRh3Bx (R = La, Gd, Lu and Sc) have been synthesized by arc melting method. Borides RRh 3Bx (R = La, Gd, Lu and Sc) have perovskite-type cubic structure: space group Pm3m; Z = 1. The lattice parameters a of the stoichiometric RRh3B for R = La, Gd, Lu and Sc are 0.4251(1), 0.4183(1), 0.4126(1) and 0.4080(1) nm, respectively. LaRh3B x does not have boron-nonstoichiometry as x = 0. In GdRh 3Bx and LuRh3Bx, boron- nonstoichiometry ranges between 0.55 ≦ x ≦ 1 and 0.30 ≦ x ≦ 1, respectively. The boron-nonstoichiometry range is the widest, 0 ≦ x ≦ 1, for R = Sc. Boron-nonstoichiometry increases with decreasing atomic radius of R. The microhardness of the stoichiometric RRh3B for R = La, Gd, Lu and Sc is 4.2 ± 0.1, 6.8 ± 0.1, 7.7 ± 0.5 and 9.9 ± 0.1 GPa, respectively. As a result, microhardness increases with decreasing atomic size of R in RRh3B; R is positioned at the eight corners of the cube in the perovskite-type structure. Thus, hardness is strongly dependent on R element. The hardness changes almost linearly with boron concentration x for R = Gd and Lu in RRh3Bx, while no linear dependency is found for R = Sc. Ab initio calculations have been performed to obtain the equilibrium lattice constants and the bulk moduli. The calculated lattice constants are in excellent agreement with experimental results.
AB - Rare earth ternary borides, RRh3Bx (R = La, Gd, Lu and Sc) have been synthesized by arc melting method. Borides RRh 3Bx (R = La, Gd, Lu and Sc) have perovskite-type cubic structure: space group Pm3m; Z = 1. The lattice parameters a of the stoichiometric RRh3B for R = La, Gd, Lu and Sc are 0.4251(1), 0.4183(1), 0.4126(1) and 0.4080(1) nm, respectively. LaRh3B x does not have boron-nonstoichiometry as x = 0. In GdRh 3Bx and LuRh3Bx, boron- nonstoichiometry ranges between 0.55 ≦ x ≦ 1 and 0.30 ≦ x ≦ 1, respectively. The boron-nonstoichiometry range is the widest, 0 ≦ x ≦ 1, for R = Sc. Boron-nonstoichiometry increases with decreasing atomic radius of R. The microhardness of the stoichiometric RRh3B for R = La, Gd, Lu and Sc is 4.2 ± 0.1, 6.8 ± 0.1, 7.7 ± 0.5 and 9.9 ± 0.1 GPa, respectively. As a result, microhardness increases with decreasing atomic size of R in RRh3B; R is positioned at the eight corners of the cube in the perovskite-type structure. Thus, hardness is strongly dependent on R element. The hardness changes almost linearly with boron concentration x for R = Gd and Lu in RRh3Bx, while no linear dependency is found for R = Sc. Ab initio calculations have been performed to obtain the equilibrium lattice constants and the bulk moduli. The calculated lattice constants are in excellent agreement with experimental results.
KW - Boron-nonstoichiometry
KW - Microhardness
KW - Perovskite-type phase
KW - RRhB (R = La, Gd, Lu and Sc)
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U2 - 10.1016/j.jallcom.2005.04.113
DO - 10.1016/j.jallcom.2005.04.113
M3 - Conference article
AN - SCOPUS:31144440551
VL - 408-412
SP - 379
EP - 383
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
SN - 0925-8388
T2 - Proceedings of the Rare Earths'04 in Nara, Japan
Y2 - 7 November 2004 through 12 November 2004
ER -