In 1911, Dutch physicist Heike Kamerlingh Onnes discovered that the resistance of mercury disappears completely at temperatures below about 4K. This phenomenon is called superconductivity; consequently, materials that have this property would be called superconductors. Thanks to this great discovery, in 1913, he won a Nobel Prize in Physics for his research in this area.[2]The technological development of superconductivity was hindered by the cost of producing the extremely low temperatures necessary to obtain the effect. As recently as 1986, new superconducting ceramic materials were discovered that have significantly higher critical transition temperatures. Gradually, as more and more metals, alloys, and compounds are discovered to have superconductivity and are cheap to produce, the practical application of room-temperature superconducting devices may become commonplace. Excellent properties and interesting prospects of superconductors have been discovered since the day they were discovered. Superconductors have been used in many fields in recent times, and this article will mainly discuss the classifications, properties, applications, etc., to help people understandBy Wang, Jack1superconductors better.2. Classification2.1 Sorted by material:Superconductors can be made of some pure elements, such as mercury and lanthanum, and some allotropes of carbon, such as graphite.[4]Some alloys such as niobium-titanium[5] also have superconducting properties. Ceramics can also be used as superconductors, such as the yttrium barium copper oxide (YBCO) family.2.2 Sorted by Meissner effect:Type I superconductors:[8]Type I superconductors all show the similar magnetization curve in a magnetic field, as shown in figure 1: ...... half of the sheet ...... the amount of Ic passing through each unit cross-sectional area of ​​the superconductor is called the critical current density, which is represented from Jc. All these critical values ​​strongly limit the conditions for using superconductors, and therefore the search for new superconductors with higher tolerances has become an important research topic for scientists. For example, from 1911, when the Dutch physicist Kamerlingh Onnes discovered the superconductivity of mercury (Tc = 4.2 K), to 1986, the highest Tc found was 23.2 K (Nb3Ge, 1973). In 1986, Swiss physicists Bednorz and Müller discovered superconductivity in a lanthanum-based cuprate perovskite material, which had a Tc of 35 K.[15] And only after a year, the new record of Tc reached around 100K. This breakthrough has opened a bright future for the application of superconductors. This led to the victory of Bednorz and Müller