918 research outputs found
Superconductivity in metal rich Li-Pd-B ternary Boride
8K superconductivity was observed in the metal rich Li-Pd-B ternary system.
Structural, microstructural, electrical and magnetic investigations for various
compositions proved that Li2Pd3B compound, which has a cubic structure composed
of distorted Pd6B octahedrons, is responsible for the superconductivity. This
is the first observation of superconductivity in metal rich ternary borides
containing alkaline metal and Pd as a late transition metal. The compound
prepared by arc melting has high density, is stable in the air and has an upper
critical field, Hc2(0), of 6T.Comment: 4 pages, 5 figur
Lithium colloids and color center creation in electron-irradiated Li2NH observed by electron-spin resonance
4 pagesInternational audienceWe have irradiated Li2NH powder with MeV electrons at room temperature and investigated the introduced defects with electron spin resonance. CESR indicates the presence of nanosize metallic Li colloids seen as a Lorentzian line with a g = 2.0023 and a line width DeltaH = 50 microT. A second, broader, signal (DeltaH = 3 to 4 mT) appears superimposed upon the Li line at low T (Curie-type behavior) which exhibits complex T-dependence with a break near 180 K for its g-value and DeltaH. We are suggesting for the latter a vacancy-type defect in the NH-sublattice, with freezing of its H-component below 180 K. When heated both the Li colloids and the color centers anneal around 100 C probably due to hydrogen evolution and subsequent chemical degradation
First-principles study on the intermediate compounds of LiBH
We report the results of the first-principles calculation on the intermediate
compounds of LiBH. The stability of LiBH and LiBH has been examined with the ultrasoft pseudopotential method based on
the density functional theory. Theoretical prediction has suggested that
monoclinic LiBH is the most stable among the candidate
materials. We propose the following hydriding/dehydriding process of LiBH
via this intermediate compound : LiBHLiBH LiH HLiH B H. The hydrogen content and enthalpy of the first
reaction are estimated to be 10 mass% and 56 kJ/mol H, respectively, and
those of the second reaction are 4 mass% and 125 kJ/mol H. They are in good
agreement with experimental results of the thermal desorption spectra of
LiBH. Our calculation has predicted that the bending modes for the
-phonon frequencies of monoclinic LiBH are lower than
that of LiBH, while stretching modes are higher. These results are very
useful for the experimental search and identification of possible intermediate
compounds.Comment: 7 pages, 5 figures, submitted to PR
Magnetization measurements on Li2Pd3B superconductor
Magnetization in DC magnetic fields and at different temperatures have been
measured on the Li2Pd3B compound. This material was recently found to show
superconductivity at 7-8K. Critical fields Hc1(0) and Hc2(0) have been
determined to be 135Oe and 4T, respectively. Critical current density, scaling
of the pinning force within the Kramer model and the irreversibility field data
are presented. Several superconductivity parameters were deduced: x(csi)=9.1
nm, l(lamda)=194nm and k=21. The material resembles other boride
superconductors from the investigated points of view.Comment: 10 pages, 5 figure
Dehydriding and rehydriding reactions of LiBHâ
Structural differences in LiBHâ before and after the melting reaction at approximately 550 K were investigated to clarify the experimental method for the confirmation of reversible dehydriding and rehydriding reactions. Since the long-range order of LiBHâ begins to disappear after the melting reaction was achieved, investigation of the atomistic vibrations of the [BHâ]-anion in LiBHâ was found to be effective for the confirmation of the reversibility. In the present study, LiBHâ was successively dehydrided (decomposed) into LiH and B under 1 MPa of hydrogen at 873 K, and then rehydrided (recombined) into LiBHâ under 35 MPa of hydrogen at the same temperature (873 K). The temperatures at the beginning and ending of the dehydriding reaction are lowered, by approximately 30 K, for LiBHâ substituted (or mixed) with Mg (atomic ratio of Li:Mg=9:1) as compared to those for LiBHâ alone. This is similar to the tendency exhibited by LiNHâ
Effect of daily oral minodronate on vertebral fractures in Japanese postmenopausal women with established osteoporosis: a randomized placebo-controlled double-blind study
Superconductivity in a new layered triangular-lattice system Li2IrSi2
We report on the crystal structure and superconducting properties of a novel iridium-silicide, namely Li2IrSi2. It has a Ag2NiO2-type structure (space group R-3m) with the lattice parameters a = 4.028 30(6) Ă
and c = 13.161 80(15) Ă
. The crystal structure comprises IrSi2 and double Li layers stacked alternately along the c-axis. The IrSi2 layer includes a two-dimensional Ir equilateral-triangular lattice. Electrical resistivity and static magnetic measurements revealed that Li2IrSi2 is a type-II superconductor with critical temperature (Tc) of 3.3 K. We estimated the following superconducting parameters: lower critical field Hc1(0) ~ 42 Oe, upper critical field Hc2(0) ~ 1.7 kOe, penetration depth λ0 ~ 265 nm, coherence length Ο0 ~ 44 nm, and GinzburgâLandau parameter ÎșGL ~ 6.02. The specific-heat data suggested that superconductivity in Li2IrSi2 could be attributed to weak-coupling Cooper pairs
Experimental and computational studies on structural transitions in the LiBH4-LiI pseudobinary system
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