Superconducting YBa₂Cu₃O_7-x

Synthetic procedure from Colin Greaves, "Structural, Electrical and Magnetic Properties of Perovskite Ceramics," in Inorganic Experiments, edited by J. Derek Woolins, Wiley-VCH, 1994, pages 265-270 (ISBN 3527305106).

The magnetic flux of a magnet will not penetrate a superconducting material, enabling a magnet to be levitated on a superconducting material. In this experiment a pellet of YBa₂Cu₃O_x is prepared and cooled to its superconducting state in liquid nitrogen. See A. B. Ellis, " Superconductors: Better levitation through chemistry," J. Chem. Educ., 64(10), 836-841 (1987).

Clicking a thumbnail on this web page (http://chemistry.beloit.edu/edetc/nanolab/YBaCuO/index.html) shows a movie of that step.

Procedure

Wear eye protection

Thermal gloves recommended

Dry reagents (Y₂O₃, CuO, and BaCO₃) in an oven at 400°C for several hours.

Weigh out a 1:2:3 molar ratio of Y:Ba:Cu (0.3023 g CuO, 0.5000 g BaCO₃,and 0.1430 g Y₂O₃). Grind the materials to mix.

Load 1/3 to 1/2 the material in a 13-mm diameter pellet die.

Press at 5000 kg in a hydraulic press.

Make two or three pellets total.

Transfer the pellets to an alumina boat and load into an open quartz tube in a tube furnace.

Heat at 930°C for 12 hours.
Cool to 500°C and hold for 1 hour.
Cool to 400°C over 30 minutes.
Remove and/or cool to room temperature

Materials

• CuO, cupric oxide, Aldrich 450812, Acros AC40586
• Y₂O₃, Aldrich 205168
• BaCO₃, Aldrich 237108, Fisher B30
• 400°C muffle furnace, crucible
• mortar and pestle
• pellet die and press
• 930°C tube furnace, alumina boat
• small magnet, tweezers, foam cup, liquid nitrogen

Properties

Cool a pellet in liquid nitrogen. An inverted foam cup makes an excellent insulating stand to hold the pellet. A magnet placed at the correct height above a superconducting pellet will levitate.

A levitating magnet supported by a superconductor can be freely spun.

Long term exposure to moisture may cause the pellet to crumble. A wax or polymer coating may help preserve the pellet.

Additional levitation movies

---