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 YBa2Cu3Ox
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).
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.