Magnesium diboride (MgB2) is a material with unique properties in condensed matter physics. Its discovery significantly impacted the scientific community, opening new avenues for research and technological development.
What is Magnesium Diboride?
Magnesium diboride (MgB2) is an inorganic compound composed of one magnesium atom and two boron atoms. It forms a simple hexagonal crystal structure, where layers of boron atoms are separated by layers of magnesium atoms.
MgB2 was unexpectedly discovered as a superconductor in 2001. This finding generated considerable excitement among researchers due to its relatively high critical temperature for a conventional superconductor.
Understanding Its Superconducting Properties
Superconductivity describes a state where certain materials exhibit zero electrical resistance and expel magnetic fields below a specific temperature. Magnesium diboride becomes superconducting at a critical temperature (Tc) of 39 Kelvin, approximately -234 degrees Celsius. This temperature is considerably higher than that of many other conventional superconductors, which often require liquid helium cooling at around 4.2 Kelvin.
The higher critical temperature of MgB2 allows cooling with less expensive and more readily available refrigerants, such as liquid hydrogen or closed-cycle cryocoolers. This reduces the complexity and cost of maintaining superconducting conditions. The mechanism behind MgB2’s superconductivity aligns with the Bardeen-Cooper-Schrieffer (BCS) theory, but with two distinct energy gaps. These two gaps, one larger and one smaller, arise from how electrons interact with vibrations in the crystal lattice, contributing to its robust superconducting performance.
Key Advantages and Applications
Magnesium diboride offers several practical advantages for various technological applications. Its constituent elements, magnesium and boron, are abundant and relatively inexpensive, making the material cost-effective to produce. Additionally, MgB2 can be fabricated into wires and tapes using conventional metallurgical techniques, simplifying its integration into existing manufacturing processes. These attributes support its potential for widespread adoption across different industries.
The properties of MgB2 make it a strong candidate for use in Magnetic Resonance Imaging (MRI) machines. Its higher critical temperature allows for simpler and more compact cooling systems, potentially reducing the overall size and operational costs of these medical devices. In the field of high-field magnets, MgB2 finds use in research facilities, particle accelerators, and fusion reactors where strong and stable magnetic fields are required. The material’s ability to carry large currents without resistance makes it efficient for these demanding applications.
Magnesium diboride also holds promise for enhancing power transmission efficiency. Superconducting power cables made from MgB2 could transmit electricity with virtually no energy loss, offering a more sustainable and efficient way to deliver power across grids. Furthermore, it is being explored for fault current limiters, which are devices designed to protect electrical grids from damaging power surges by rapidly switching between superconducting and resistive states. Its application extends to sensitive sensors and detectors, including terahertz detectors and bolometers, which benefit from its low noise and high sensitivity at specific operating temperatures.
References
Superconducting magnesium diboride: a brief review. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 374(20150172), 20150172.
Applications of MgB2. Superconductor Science and Technology, 20(12), R125.