| Budget Amount *help |
¥15,300,000 (Direct Cost: ¥15,300,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2005: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2004: ¥10,200,000 (Direct Cost: ¥10,200,000)
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| Research Abstract |
In this study, we synthesized the C32-type ternary silicides and their related materials and measured their physical properties. In the study on ternary silicides with the C32-type structure, we investigated the effect of substitution of Ga atoms by Zn atoms in CaGaSi, and phase relationship and electrical resistivity of the ternary silicides LaAl_<2-x>Si_x with x ranging from 0 to 1.03. The crystal structure of LaAl<2-x>Si_x depends on the Si content x : the Cu_2Mg-type structure for 0 = x = 0.005, the A1B_2-type for 0.14 = x = 0.62, and the α-ThSi_2-type for 0.72 = x = 1.03. The range of x at which the AlB_2 phase LaAl<2-x>Si_x appears was wider than that reported previously. In the AlB_2 phase, the lattice constants a and c change anisotropically with x : a decreases with x while c increases with x. On the other hand, in the α-ThSi_2 phase, both a and c decrease with x. The electrical resistivity measurements at temperatures ranging from 2 to 300 K revealed that the AlB_2 phase and the α-ThSi_2 phase LaAl<2-x>Si_x, are metals that does not show a superconductivity down to 2 K. In the study on the related materials, we investigated CaAl_2Si_2, SrSi_2, and a superconducting filled skuterudite La_<0.8>Rh_4P_<12>. La_<0.8>Rh_4P_<12> is a type-II superconducting material with a critical temperature for the superconducting transition, Tc, of 14.9 K. The upper critical field Hc_2(0) and Ginzburg-Landau coherent length ζ(0) were determined to be 167(1) kOe and 4.41(1) nm, respectively. The electronic heat capacity coefficient, γ_n, and the Debye temperature, Θ_D, were 25.1(8) mJ/molK^2 and 459(12) K, respectively. Using T_c and Θ_D, the electron-phonon coupling constant, λ, was estimated to be approximately 0.7, suggesting that La_<0.8>Rh_4P_<12> is an intermediate-coupling superconducting material.
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