Electron beam is required to melt and sinter powders: melting for shaping while sintering for fixing the powder at a powder bed when required. The beam is generated by electrically heating a cathode made from a material having a high melting point and low work function. Due to the high melting point, the cathode does not melt and degrade during electron generation, while due to the low work function, electrons detach from the cathode at a low applied voltage. Work function is a physics term that states how much voltage needs to be applied to a material to detach an electron from its surface. The lower the work function, the better the material for e-beam generation. Tungsten (W) and lanthanum hexaboride (LaB6) are used as a cathode material, each of which has a melting point and work function of 3422 °C, 4.5 eV, and 2210 °C, 2.5 eV, respectively. W is used because of its high melting point, while LaB6 used because of its lower work function and higher lifetime as a cathode. Besides generating a beam by heating the cathode, which is called thermionic emission, it is generated by creating plasma between the cathode and the anode. The beam, thus produced, is used in AM.