Study of Boron Based Superconductivity and Effect of High Temperature Cuprate Superconductors

Abstract

This paper illustrates the main normal and Boron superconducting state temperature properties of magnesium diboride, a substance known since early 1950's, but lately graded to be superconductive at a remarkably high critical temperature Tc=40K a binary synthesis. What makes MgB2 so special? Its high Tc, simple crystal construction, large coherence lengths, high serious current densities and fields, lucidity of surface boundaries to current promises that MgB2 will be a good material both large scale applications and electronic devices. Throughout the last seven month, MgB2 has been fabricated in various shape, bulk, single crystals, thin films, ribbons and wires. The largest critical current densities >10MA/cm2 and critical fields 40T are achieved thin films. The anisotropy attribution inferred from upper critical field measurements is still to be resolved, a wide range of values being reported, γ = 1.2 ÷ 9. Also there is no consensus about the existence of a single anisotropic or double energy cavity. One central issue is whether or not MgB2 represents a new class of superconductors, being the tip of an iceberg that waits to be discovered. Until now MgB2 holds the record of the highest Tc among simple binary synthesis. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search superconductivity in related materials, several synthesis being already announced to become superconductive: TaB2, BeB2.75, C-S composites, and the elemental B under pressure. I. INTRODUCTIN High-temperature superconductors (abbreviated high-Tc or HTS) are materials that behave as superconductors at unusually high temperatures. The highest -Tc superconductor was discovered in 1986 by IBM researchers Karl Muller and Johannes Bednorz, who were awarded the 1987 Nobel Prize in Physics for their important break-through in the discovery of superconductivity in ceramic materials. Until 2008, only certain compounds of copper and oxygen (so-called cuprates) were believed to have HTS properties, and the term high-temperature superconductor was used interchangeably with cuprate superconductor compounds such as bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO). However, several iron-based compounds (the iron pnictides) are now known to be superconducting at high temperatures. Some cuprates have an upper critical field of 100 tesla. However, cuprate materials are brittle ceramics which are expensive to manufacture and not easily turned into wires or other useful shapes. In 2004, bridging the gap unraveling the super hardness and the superconducting communities, Ekimov et al exposed the superconducting behaviour of a diamond sample resulting from annealing graphite with B4C at 2500-2800 K under 8-9 GPa 5s. These authors planned also a mechanism the transformation of graphite into diamond at high pressure and high temperature (HPHT), and made a careful characterization of the diamond polycrystal . Similar results be reported shortly after polycrystalline and (100)-oriented single crystaldiamond films full-fledged by microwave plasma-assisted chemical vapour deposition (MPCVD), showing that zero resistivity could be experiential up to the boiling temperature of helium (4.2 K), that doping-induced superconductivity appeared above about 6 1020 B/cm3 and that Tc amplified with the Boron concentration.