what is Thermo electric series?

In the production of thermo emf the thermocouple produce the current without a cell so to know the direction of current Seebeck made an arrangement of metals in series called thermoelectric series.

Antimony, Iron, Zinc, Silver, Lead, Copper, Platinum, Nickel, Bismuth

The direction of current is from earlier metal to the later one of thermoelectric series in cold junction and as the separation between any two metals of the series increases the thermo emf also increases. Eg. Iron-Copper provides high emf than Iron-Zinc.