Since Heike Kamerlingh Onnes discovered superconductivity in 1911, all superconductors known up until the time of the Bednorz and Müller's discovery lost their electrical resistance and entered the superconducting state at temperatures barely above absolute zero. These early superconductors were made of metals or semiconducting alloys, but Bednorz and Müller managed to achieve superconductivity at temperatures higher than any previously possible by using ceramics made from metallic oxide mixtures. When they announced their findings, which were quickly confirmed by other laboratories, a race to produce superconductors with higher and higher critical temperatures (the point at which the resistance of a material drops to zero) began.
Born in Germany as Johannes Georg Bednorz on May 16, 1950, Bednorz was one of several children of Anton and Elisabeth Bednorz. Both parents were teachers, his father working in a primary school and his mother giving piano lessons. Although his parents attempted to direct him towards the study of classical music, Bednorz’s inclinations were of a more practical nature. In addition to mechanics, he developed an interest in chemistry, a subject that could be largely explored in a hands-on way through experimentation.
When Bednorz began his college career at the University of Münster in 1968, he initially chose to major in chemistry. But because he was unhappy with the large classes, Bednorz changed his focus to crystallography, a less popular field, but one that seemed well suited to his interests. In 1972, Bednorz spent the summer in Zürich, Switzerland, as a visiting student at the IBM Research Laboratory. The experience greatly impacted the direction his career would take, because there he met Müller, who headed the lab’s physics department. Moreover, the atmosphere at IBM cultivated a sense of creative freedom in Bednorz that he later credited with helping him address research challenges in innovative ways.
While in Zürich, Bednorz learned methods of crystal production and how to characterize materials. He found the experience so rewarding that he returned in 1974 to do experimental work with perovskites, a large family of crystalline ceramics. Müller, himself greatly interested in perovskites, urged Bednorz’s continued research of the materials. Bednorz received a master’s degree from the University of Münster in 1976, and relocated to Zürich the next year to study at the Swiss Federal Institute of Technology (ETH). As Müller had hoped, Bednorz concentrated his doctoral research on the production and characterization of perovskites. Müller and Heini Gränicher supervised the work, for which Bednorz earned his Ph.D. in 1982.
With doctorate in hand, Bednorz accepted a full-time position at the IBM Zürich Research Laboratory. As colleagues, Bednorz and Müller began a concerted effort to find superconducting oxides. Bednorz chiefly functioned in an experimental capacity, preparing and testing the oxides, which he fired as ceramics because the process was less complicated and time-consuming than growing them as crystals. Müller, on the other hand, provided the theoretical basis upon which Bednorz built his experiments. After a few years of finding out what did not work, rather than finding what did, Bednorz came across an article written by French researchers that described a compound of copper and oxygen with trace amounts of barium and lanthanum. The researchers had not tested the material to determine whether or not it was superconductive, but Bednorz believed that the compound was just what he and Müller had been looking for.
In early 1986, Bednorz prepared a sample of the copper oxide he had read about and cooled it in order to test for superconductivity. The test indicated a sharp drop in electrical resistance at -262 degrees Celsius. The encouraging result inspired Bednorz to slightly modify the compound and his technique for producing it, resulting in even better results. Eventually he managed to raise the critical temperature of the compound to -238 degrees Celsius, a new record. Bednorz and Müller published their findings in April 1986 in the German journal Zeitschrift für Physik, although they had some misgivings about doing so because they had not yet tested their record-breaking copper oxide for the Meissner effect, a determining factor in whether or not a material is a true superconductor. Not surprisingly, some scientists were initially skeptical of the claims made by Bednorz and Müller, but it was not long before a research group at the University of Tokyo published exhaustive Meissner-effect data on the Bednorz- Müller copper oxide, helping quash any doubts regarding their work.
Labs around the world subsequently began producing their own metallic oxides in an effort to raise obtainable critical temperatures high enough to make superconductors practical for commercial use. A particularly important breakthrough was made when a group at the University of Houston first raised the critical temperature of a compound similar to Bednorz and Müller’s high enough to use liquid nitrogen, rather than the much more costly liquid helium, as a refrigerant.
The enthusiasm generated by the work of Bednorz and Müller is evidenced by an unusual move by the Nobel Prize Committee, which decided to award the pair the Nobel Prize in Physics in 1987, less than two years after they carried out their groundbreaking work. Most recipients have a much longer wait before their research garners the honor. Bednorz, now an IBM Fellow, continues to study and improve oxide compounds. In addition to the Nobel Prize, he has received many other awards from scientific societies and foundations across the globe.
