Milestones:Superconductivity at 93 Kelvin, 1987


Date Dedicated
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Huntsville, AL
IEEE Regions
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Discovery of Superconductivity at 93 K in Yttrium Barium Copper Oxide, 1987


On this site, a material consisting of yttrium, barium, copper, and oxygen was first conceived, synthesized, tested, and -- on 29 January 1987 -- found to exhibit stable and reproducible superconductivity at 93 Kelvin. This marked the first time the phenomenon had been unambiguously achieved above 77 Kelvin, the boiling point of liquid nitrogen, thus enabling more practical and widespread use of superconductors.

Street address(es) and GPS coordinates of the Milestone Plaque Sites

Wilson Hall (formerly the University of Alabama at Huntsville Science Building) 301 Sparkman Drive Huntsville, AL 35899 GPS Coordinates: +34.72937,-86.64147, Wilson Hall (formerly the University of Alabama at Huntsville Science Building) 301 Sparkman Drive, Huntsville, AL 35899 GPS Coordinates: +34.72937,-86.64147

Details of the physical location of the plaque

The plaque will be mounted on an interior hallway wall outside the former lab near an existing plaque commemorating the tenth anniversary of the discovery.

How the plaque site is protected/secured

The intended plaque site is on the University of Alabama in Huntsville campus which is protected by the UAH Campus Police. The building in which the plaque will be installed is secured during nighttime hours but is open to the public seven days a week from 6:30 a.m. to 11:00 p.m.

Historical significance of the work

January 29th, 2017 marked the 30th anniversary of the discovery of superconductivity above the boiling point of nitrogen by Jim Ashburn, C. J. Torng, and M. K. Wu at the University of Alabama in Huntsville [1]. Surpassing 77 Kelvin had long been a key milestone on the quest for room-temperature superconductivity as it enables significantly less difficult and more cost-effective refrigeration, thus greatly expanding the prospects for more extensive use of superconductivity.

Building on the work of Johannes Georg Bednorz and Karl Alex Müller, who shared the 1987 Nobel Prize in Physics for discovering the first so-called copper oxide superconductor at about 30 Kelvin, Ashburn noted a relationship between the critical temperatures and ionic radii in a series of superconductors ranging from 20 to 40 Kelvin from which he formulated Y(1.2)Ba(0.8)CuO(4-y) [2-8]. The first sample was synthesized by Torng on 28 January 1987 and tested the following day by Ashburn and Wu. The initial AC resistivity test, marked as completing at 2:08 p.m., showed a resistive transition starting near 90 Kelvin and reaching zero (within the precision of the instruments) about 55 Kelvin. A series of seven additional tests on samples made that evening, many reaching zero above 77 Kelvin. Ashburn’s dissertation records, “In all, eight tests on four samples from three separate batches were performed that day. All showed transitions with onsets ranging upwards from 89 K and averaging 93 K and midpoints nearing 93 K" [9]. Superconductivity was subsequently confirmed in these samples via field effect and magnetic susceptibility measurements conducted at the University of Houston the following day [10-13]. The critical superconducting phase, YBa(2)Cu(3)O(7), was subsequently isolated and identified by several groups during the weeks to follow.

Due to a quantum mechanical phenomenon whereby electrons bind in pairs, superconductors display a number of remarkable properties, most notably zero DC resistance while conducting very high density currents, thus enabling the transmission of significant electrical power and the generation of powerful magnetic fields. In addition to high current/high field applications, superconductors also have advantages in signal detection, combining low noise and dispersion with very high sensitivity.

Features that set this work apart from similar achievements

As of the mid-70s, the highest confirmed critical temperature of a superconductor was approximately 23 K, a mark reached over decades, often by fractions of a Kelvin at a time. The 23 K record stood for over a dozen years before Bednorz and Muller shattered it with ~30K superconductivity in LBCO. YBCO, in turn, tripled that level at 93 K. At the same time, it marked a somewhat unique material in that the layered structure was the consequence of the ordering of yttrium and barium and, furthermore, YBCO is characterized as a "self-doped" material, also distinguishing it from LBCO.

The Hor v. Chu case was resolved in April of 2016. In the case, Hor was challenging Chu’s inventorship on both YBCO and its subsequent rare earth analogs. As the proceedings continued, Hor shifted his emphasis to the rare earth variants of YBCO. Here is a link to the final decision in the Hor v. Chu case:

University of Alabama Huntsville settled with University of Houston in 2002(?).

Significant references

[1] M. K. Wu, J. R. Ashburn, C. J. Torng, P. H. Hor, R. L. Meng, L. Gao, Z. J. Huang, Y. Q. Wang, and C. W. Chu (1987). "Superconductivity at 93 K in a New Mixed Phase Y-Ba-Cu-O Compound System at Ambient Pressure,” Phys. Rev. Lett. 58 (9): 9089 (1987).

[2] Robert Pool. “Superconductor Credits Bypass Alabama.” Science 5 (August 1988): 655-657.

[3] “What Happened Next? -- Updates on the TJ Retrospective.” Taiwan Today (30 March 2007). <>.

[4] James D. Doss. Engineer's Guide to High-Temperature Superconductivity. New York, Wiley-Interscience, 1989.

[5] Jean Matricon and Georges Waysand. The Cold Wars: A History of Superconductivity. Rutgers University Press, 2003. [6] Bruce Schechter. The Path of No Resistance: The Story of the Revolution in Superconductivity. New York, Simon & Schuster, 1989.

[10] C. W. Chu. “High Temperature Superconductivity.” History of Original Ideas and Basic Discoveries in Particle Physics. Ed. H. B. Newman, T. Ypsilantis. New York: Plenum, 1996. 793.

[11] C. W. Chu. “Superconductivity Above 90 K and Beyond.” Proceedings of the 10th Anniversary HTS Workshop on Physics, Materials and Applications. Ed. B. Batlogg, C. W. Chu, W. K. Chu, D. U. Gubser, K. A. Müller. Singapore: World Scientific, 1996. 17.

[12] C. W. Chu. “High-Temperature Superconducting Materials: A Decade of Impressive Advancement of Tc.” IEEE Transactions on Applied Superconductivity 7.2 (1997): 80-89.

[13] While the above three sources confirm the date and location of the discovery, their descriptions of how the critical YBCO composition was conceived are in error. See James Ashburn. Discovery of Superconductivity at 93 K in YBCO: The View from Ground Zero. <>.

Supporting materials

[7] Alabama Historical Commission Marker: Superconductivity Discovery. Wilson Hall. Dedicated 29 January 2012. <>. Media:07_AlabamaHistoricalCommissionMarker.jpg

[8] The University of Alabama in Huntsville Marker: Superconductivity Advance. Wilson Hall. Dedicated 29 January 1997. Media:08_UAHMarker-a.jpg Media:08_UAHMarker-b.jpg Media:08_UAHMarker-c.jpg Media:08_UAHMarker-d.jpg

[9] J. R. Ashburn. Yttrium Barium Copper Oxide: The Formulation and Magnetic Properties of a 93 K Superconductor. Huntsville, AL: UAH (December 1990). Media:09_AshburnDissertationCh2.pdf.


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