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).

Procedure

Wear eye protection

Thermal gloves recommended

Dry reagents (Y₂O₃, CuO, and BaCO₃) in an oven at 400 degrees 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 degrees C for 12 hours.
Cool to 500 degrees C and hold for 1 hour.
Cool to 400 degrees C over 30 minutes.
Remove and/or cool to room temperature

Materials

Y₂O₃, CuO, and BaCO₃
muffle furnace, crucible
pellet press
tube furnace, alumina boat
small magnet, 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 about a superconducting pellet will levitate.
Larger movie

A levitating magnet supported by a supperconductor can be freely spun.
Larger movie

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

Additional levitation movies

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