High-temperature superconductivity (high-Tc or HTS) is superconductivity in materials with a critical temperature (the temperature below which the material behaves as a superconductor) above 77 K (−196.2 °C; −321.1 °F), the boiling point of liquid nitrogen. They are "high-temperature" only relative to previously known superconductors, which function only closer to absolute zero. The first high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller. Although the critical temperature is around 35.1 K (−238.1 °C; −396.5 °F), this material was modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature 93 K (−180.2 °C; −292.3 °F). Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-Tc materials are type-II superconductors.
The major advantage of high-temperature superconductors is that they can be cooled using liquid nitrogen, in contrast to previously known superconductors, which require expensive and hard-to-handle coolants, primarily liquid helium. A second advantage of high-Tc materials is they retain their superconductivity in higher magnetic fields than previous materials. This is important when constructing superconducting magnets, a primary application of high-Tc materials.