Key Vocabulary:
Meissner effect: repels all magnetic force on the below-critical temperature
YBCO: Yttrium Barium Copper Oxide
Circuit: passages for electric current to circulate
Resistance: a measure of the opposition to current flow in an electrical circuit
Dielectric: materials that do not flow any electric current
Diamagnetic: materials that are not usually magnetic
Electromagnetic: any fields related to both electric and magnetic
Flux pinning: Links
Compound: chemically bonded among two or more elements
What is a superconductor?
Superconductors refer to materials that have no electrical resistance. More interestingly, superconductors also possess characteristics of diamagnetic: materials that are usually not magnetized but potentially reach temporal magnetism. Basically, the purpose of a superconductor is to flow electric current in the circuit without any energy loss. For example, it is indispensable for the remote controller to function properly. If the battery in the remote controller runs out of energy, then people need to replace the new batteries with old ones. However, in the future, with superconductors, any energy source becomes “permanent batteries”. Common electricity devices usually possess their own resistivity to interfere with the flow of electric current in the circuit. The resistance causes energy loss through heat and sound. On the contrary, superconductors do not possess internal resistance. In other words, superconductors do not waste energy while effectively transferring electric current in a desirable location.
Limitation of superconductor
As aforementioned, superconductors would effectively function as electronic devices without loss of energy. Then, why do not modern societies actively use superconductors? Well, interactions among electrons in circuits impede current flow, causing resistance in circuits. To remedy this problem, the temperature should be extremely low: approximately 0 K (-273.15 °C). Therefore, with the current technology, it is hard to find appropriate materials for superconductors in electronic devices and at room temperature. Also, it is unrealistic to keep a low temperature for superconductors. The purpose of superconductors is to save money, but the expense of maintaining low temperatures is even higher.
Potential superconductor (1)
Scientists have worked to invent compounds for the potential usage of superconductors. In 1986, scientists Georg Bednorz and K. Alex Müller found La2CuO4, which can function at the temperature of 35 K. At the above critical temperature, the material behaves as diamagnetic, which are freely magnetized when placed in the magnetic field and create magnetic fields that are opposite direction existed magnetic fields. Interestingly, at room temperature, any magnet above superconductors is able to be levitated. In other words, the repulsion magnetic force is large enough to withstand the gravity force of a magnet in some cases. For example, the maglev train is levitated with the power of electromagnetic to run the train without any friction, so the train can travel much faster than other trains. Meanwhile, at the below-critical temperature (35 K), La2CuO4 becomes a nonresistance superconductor.
Figure 3: the magnetic field is allowed to pass through
the superconductor. But when the superconductor is
below the critical temperature, the magnetic field lines
are bent around it.
YBCO Superconductor
In the following year, scientists Paul Chu and his companions finally discovered YBa2Cu3O7. The critical temperature of YBa2Cu3O7 (77 K) is even higher but cheaper than that of La2CuO4. Scientists conduct an experiment if YBCO is a true superconductor. Basically, the way scientists verify was very simple. If the magnet floats up above YBCO just like in the below picture, it proves that YBCO is a superconductor. If you know about this more specifically, watch the following video: Making superconductors. Procedures to create YBCO needs to be delineated and complicated. First, the ratio between yttrium, barium, and copper should be 1:2:3. If not, there would be some remnant after the reaction, which might be mixed with and disrupt the target compound. Furthermore, 7 oxygen molecules need to be attached to YBCO. If only 6 of them are attached, then not only magnetic field would be very weak but also the materials themselves would be brittle as well. However, ensuring 7 oxygen molecules on the compound is tough. That is because scientists require really high pressure to form YBa2Cu3O7.
Figure 5: this seems like computer graphics, but it is not. Superconductors are able to lift magnet with magnetic force to cancel out gravity force.
Abstract
Despite the emergence of YBCO conductors, humans are still impossible to apply superconductors to electronic devices, which would be the final destination of this technology. Scientists currently endeavor to find out chemical materials that can function as superconductors at room temperature and history made progress by the higher critical temperatures of superconductors. I believe that scientists will be able to find superconductors that possess higher critical temperatures than room temperature.
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