In the extraction of aluminium by Hall-Heroult process, purified Al2O3 is mixed with CaF2 to
Al2O3 is a bad conductor of electricity and have very high meting point.
Thus, CaF2 and Na3AlF6 are used in Hall-Heroult’s process to extract Al from Al2O3. They lower the melting point of Al2O3 and increase the conductivity of the molten mixture.