Superconductors
Step 2 - Activities
Preparation of a high temperature superconductor: YBCO (YBa2Cu3O7); magnetic levitation
In order to synthesize YBCO you need:
- Y2O3;
- BaO2;
- CuO;
- an agate mortar;
- an alumina crucible;
- a furnace that can be heated up to 1000°C where O2 can flow;
- a press;
- a pellet press.
For the magnetic levitation you need:
- a plastic or metallic container;
- liquid nitrogen;
- an YBCO pellet;
- a small Nd-Fe-B magnet.
Activity 1) YBCO preparation
Weigh the calculated amount of each reagent and mix thoroughly (at least for a quarter of an hour) the powders in the mortar. At the end of the mixing phase put the powders in the crucible and perform the first thermal treatment at 910°C in flowing O2 for 15 hours (heating rate: 100°C/min; cooling rate: 150°C/min).
On the next day extract the powders, mix them again, press them into a pellet using the pellet press. Put the pellet into the crucible and again into the furnace heating up to 950°C for 15 hours in flowing O2, with the same heating and cooling rates.
On the third day repeat the same operations: extract the powders, grind the pellet and mix the powders, press the powders into a pellet and put the pellet into the furnace; heat up to 980°C for 15 hours in flowing O2, with the same heating and cooling rates.
On the next day repeat again the same operations and heat the furnace up to 980°C for 15 hours in flowing O2, with the same heating and cooling rates.
Activity 2) Magnetic levitation
At the end of the thermal treatments, in order to verify whether the sample obtained is really superconducting, perform the experiment of magnetic levitation. Put the YBCO pellet in the container and pour liquid N2 over it (pay attention: DO NOT touch liquid N2 with your hands!). When N2 stops boiling, the sample will be at 77K, the boiling point of N2. Place gently the magnet over the YBCO pellet: if the compound is superconducting, the magnet will float over the pellet without touching it until the latter will remain in the superconducting state.
