Preparation and properties of high-Tc Nb–Ge films

Abstract

Using a previously reported low-energy sputtering technique, Nb-Ge films have been prepared with superconducting T c 's up to ~ 23 K. High-field, x-ray, and annealing results are reported for these highest-T c films. A discussion of the critical parameters required to achieve the highest transition temperatures in the Nb-Ge system is given. Also further arguments in support of the theories that these highest T c 's are due to the formation of the stoichiometric NbJGe phase in the sputtered films are presented.

Superconducting properties of MgB2 bulk materials prepared by high-pressure sintering

“…The transition temperature Tc is extremely higher than those previously reported for Nb3Ge(Tc=23.2K) 2 and YPd2B2C(Tc=23K) 3 as the highest Tc values in A15 intermetallic compounds and intermetallic borocarbides, respectively. The discovery seems to confirm the speculation that the low mass of boron should be conducive to high phonon frequencies and consequently high temperature superconductivity.…”

Electronic State Distributions of YBa2Cu3O7-x Laser-Ablated Plumes

“…35. In general, the error bars are comparable in value to the magnitude of the y-intercepts, making it questionable to draw inferences regarding changes in plume stoichiometry.…”

“…Although Ginzburg did not specifically prescribe cuprate oxides in his mechanism, it did anticipate by a few years the discovery of high temperature superconductivity. [41] The first breakthrough towards high temperature superconductivity, commonly defined as a superconducting state at liquid nitrogen temperatures, came with Bednorz and Muller's discovery of superconductivity in LBCO at 28 K. [12] This was not much higher than the previous record of 23 K in Nb 3 Ge, [35] but significance of the discovery was profound because it occurred in an oxide instead of a metal, which opened up a new category of materials for study. This discovery was soon followed by …”

Quaternary borocarbides: Relatively high T intermetallic superconductors and magnetic superconductors

“…This instability of the structure is consistent with the belief that in intermetallic superconductors, higher the T c , lesser is the structural stability. For example, Nb 3 Ge, the superconductor with the previously known highest T c (23 K), does not form in bulk, but only in thin film form [63]. Of course, the superconductor MgB 2 with T c $ 39 K [10], discovered after QBC, is an extraordinary exception.…”