Photoelectric and Thermionic Properties of Nickel

The photoelectric and thermionic properties of spectroscopically pure nickel were studied through a wide range of temperatures including the Curie temperature, 350°C. The samples were studied after having been subjected to long outgassing processes. A marked change occurs in the slope of the temperature-photoelectric current curves at the Curie temperature. This change is accounted for by an increase in the work function and a change in the probability factor $\alpha$. The work function of carefully outgassed nickel was found to be 5.05±0.05 electron volts below 623°K. At this temperature the work function increases becoming 5.20±0.05 electron volts at 1108°K. A work function of 5.24 electron volts was determined thermionically at temperatures of 1150°K and above.