Superconductors

By: Luke Grocholl, Chemfiles Volume 5 Article 13

Luke Grocholl, Ph.D.
Materials Science Team
Sigma-Aldrich Corporation

Superconductors are materials that exhibit zero electrical resistance below a certain temperature defined as the critical temperature (TC). Prior to 1986, the highest TC reported was 20 K for Nb3Ge and Nb3Sn.1 During 1986–87, a group led by Johannes Bednorz and Karl Müller reported the ceramic oxides La2–xBaxCuO4–x and YBa2Cu3O7 (Sigma-Aldrich Cat. No. 328626) superconduct above the boiling point of nitrogen (77 K).2,3 Materials whose TC is greater than the boiling point of nitrogen (a common, readily available, cryogenic coolant) are referred to as high-temperature superconductors (HTS). Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 for their work.

Cuprate materials dominate the field of high-temperature superconductors. Their discovery in 1986 led to a flood of activity and dozens of mixed-metal cuprates were synthesized with everincreasing TC’s. These materials are generally characterized as perovskites as they possess a roughly two-metal to three-oxygen ratio. Typical HTS perovskites are mixtures of metals with at least one rare-earth or late p-block metal with a cuprate (copper oxide). Current theory holds that the copper and oxygen atoms will be held in one or more planes in the unit cell. Superconductivity arises from electron interactions in the Cu–O plane. Addition of various other metals to the cuprate is believed to create holes in the Cu–O plane, resulting in new electronic ordered states including a hightemperature superconducting state.

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Oxides



Name Formula MW CAS MP BP Density at 25 °C Cat. No.
Antimony(III) oxide, 99.999% Sb2O3 291.52 [1309-64-4] 655 °C 1550 °C   202649-10G
202649-50G
Barium oxide, 99.99% BaO 153.34 [1304-28-5] 1973 °C 2000 °C 5.72 g/mL 554847-5G
554847-25G
Bismuth(III) oxide, 99.999% Bi2O3 465.96 [1304-76-3] 817 °C 1890 °C 8.0 g/mL 202827-10G
202827-50G
202827-250G
Calcium oxide, 99.995% CaO 56.08 [1305-78-8] 2850 °C   3.3 g/mL 229539-5G
229539-50G
Cerium(IV) oxide, 99.995% CeO2 172.12 [1306-38-3] 2400 °C   7.13 g/mL 202975-10G
202975-50G
Copper(II) oxide, 99.9999% CuO 79.54 [1317-38-0] 1336 °C   6.31 g/mL 203130-5G
203130-25G
203130-100G
Europium(III) oxide, 99.999% Eu2O3 351.92 [1308-96-9] 2350 °C   7.42 g/mL 323543-1G
323543-5G
Gadolinium(III) oxide, 99.99+% Gd2O3 362.50 [12064-62-9] 2330 °C   7.407 g/mL
at 20 °C
203297-5G
203297-25G
Gold(III) oxide hydrate Au2O3 · xH2O 441.93 [1303-58-8] 150 °C (dec.)     334057-500MG
334057-2.5G
Indium(III) oxide, 99.999% In2O3 277.64 [1312-43-2] 1913 °C   7.18 g/mL 203424-5G
203424-25G
Lanthanum(III) oxide, 99.999% La2O3 325.82 [1312-81-8] 2305 °C 4200 °C 6.51 g/mL 203556-20G
203556-100G
203556-500G
Mercury(II) oxide, 99.999% HgO 216.59 [21908-53-2] 500 °C (dec.)   11.14 g/mL 203793-2G
203793-10G
Neodymium(III) oxide, 99.99% Nd2O3 336.48 [1313-97-9] 2320 °C   7.24 g/mL
at 20 °C
203858-10G
203858-50G
Strontium oxide, 99.9% SrO 103.62 [1314-11-0] 2530 °C 3000 °C 4.7 g/mL 415138-10G
415138-50G
Thallium(III) oxide, 99.99% Tl2O3 456.74 [1314-32-5] 717 °C 875 °C 10.2 g/mL 204617-10G
204617-50G
Thulium(III) oxide, 99.99% Tm2O3 385.87 [12036-44-1] 2425 °C   8.6 g/mL 204676-1G
204676-5G
Tin(IV) oxide, 99.995+% SnO2 150.69 [18282-10-5] 1630 °C 1900 °C 6.95 g/mL 204714-5G
204714-25G
Ytterbium(III) oxide, 99.99% Yb2O3 394.08 [1314-37-0] 2435 °C   19.7 g/mL 204889-2G
204889-10G
Yttrium(III) oxide, 99.999% Y2O3 225.81 [1314-36-9] 2690 °C 4300 °C 5.01 g/mL 204927-2G
204927-10G
204927-50G

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Materials

     

References

  1. Gavaler, J. R. Appl. Phys. Lett. 1973, 23, 480.
  2. Wu, M. K. et al. Phys. Rev. Lett. 1987, 58, 908.
  3. Beno, M. A. et al. Appl. Phys. Lett. 1987, 51, 57.

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