相关论文: Superconducting properties and c-axis superstructu…

The physical property characterization of Al doped Mg1-xAlxB2 system with x = 0.0 to 0.50 is reported. The results related to phase formation, structural transition, resistivity R(T) and magnetization M(T) measurements are discussed in…

In this paper, we reported the structural properties and superconductivity of Mg(B1-xCx)2 compounds. Powder x-ray diffraction results indicate that the samples crystallize in a hexagonal AlB2-type structure. Due to the chemical activity of…

We prepared MgB$_{2-x}$Be$_{x}$ ($x=0$, 0.2, 0.3, 0.4, and 0.6) samples where B is substituted with Be. MgB$_{2}$ structure is maintained up to $x=0.6$. In-plane and inter-plane lattice constants were found to decrease and increase,…

From systematic ab initio calculations of the alloy system Mg_{1-x}Al_{x}B_2, we find a strong tendency for the formation of a superstructure characterized by Al-rich layers. We also present a simple model, based on calculated energies and…

The basic magnetic and electronic properties of most binary compounds have been well known for decades. Therefore the recent announcement of superconductivity at 39 K in the simple binary ceramic compound MgB2 is surprising. This compound,…

Superconductivity and structural properties of Mg1-xAlxB2 materials have been systematically investigated. Evident modifications in both superconductivity and microstructure are identified to originate from the Al ordering along the c-axis…

Electron diffraction and high resolution microscopy have been performed on Mg1-xAlxB2 with x~0.5. This composition displays a superstructure with a repeat period of exactly 2c along the c axis and about 10 nm in the a-b plane. The…

We report a detailed study of the electronic structure of the MgB$_{2}$ with different lattice constants by using the full-potential linearized augmented plane wave(FPLAPW) method. It is found that the lattice parameters have great effect…

Precise structural information on the Mg1-xAlxB2 superconductors in the vicinity of x 0.5 is derived from high-resolution synchrotron X-ray powder diffraction measurements. We find that a hexagonal superstructure, accompanied by doubling of…

We have determined the structural properties of the superconducting compound MgB2 as a function of temperature from 11 K to 297 K and as a function of hydrostatic pressure up to 0.62 GPa using neutron powder diffraction. This compound, when…

We report that the ternary MgB2-xCx compounds adopt an isostructural AlB2-type hexagonal structure in a relatively small range of nominal carbon concentration, x<0.1. The lattice parameter a decreases almost linearly with increasing carbon…

We report the preparation of Mg1-xLixB2 compounds. Nearly single phased samples were obtained for x<0.3. The in-plane lattice parameter a decreases with Li doping, while the lattice parameter c does not show obvious change. The…

We have studied the variation of Tc with charge density and lattice parameters in Mg1-xAlxB2 superconducting samples at low Al doping x<8%. We show that high Tc occurs where the chemical potential is tuned at a "superconducting shape…

We have studied the changes in the electronic structure and the superconducting transition temperature T_c of Mg(B_{1-x}C_{x})_{2} alloys as a function of x with 0\leq x\leq 0.3. Our density-functional-based approach uses coherent-potential…

Single crystals of Mg1-xAlxB2 have been grown at a pressure of 30 kbar using the cubic anvil technique. Precipitation free crystals with x < 0.1 were obtained as a result of optimization of already developed MgB2 crystal growth procedure.…

The normal state and superconducting properties of MgB2 and Mg1-xAlxB2 are discussed based on structural, transport, and high pressure experiments. The positive Seebeck coefficient and its linear temperature dependence for Tc<T<160 K…

We report variation of lattice structure in diborides (AB2) with different A atoms to identify the special case of MgB2 showing high Tc superconductivity. High purity MgB2 (Tc~39 K) has been prepared by direct reaction of the elements and…

We have studied the structural and electronic properties of Mg(1-x)Al(x)B2 within the Virtual Crystal Approximation (VCA) by means of first-principles total-energy calculations. Results for the lattice parameters, the electronic band…

Superconducting transition temperatures ($T_c$'s) of MgB$_2$, Mg$_{1-x}$Ca$_x$B$_2$, Mg$_{1-x}$Na$_x$B$_2$, and Mg$_{1-x}$Al$_x$B$_2$ are studied within the McMillan approximation using electronic and structural information obtained from…

We have measured the thermoelectric power, S, and resistivity, rho, of pure and Al-doped MgB2. S is positive and increases linearly with temperature above the superconducting transition temperature, Tc. Deviations from the linear dependence…