Why is tungsten a suitable emitter material for thermionic power converters?

Tungsten is a highly suitable emitter material for thermionic power converters primarily due to its ability to operate reliably at very high temperatures.1

This thermal resilience is critical because the rate of thermionic emission increases rapidly as the temperature of the emitter rises. Tungsten possesses the highest melting point of all metals—3,410 °C (6,170 °F)—which allows it to withstand the extreme heat required for efficient electron emission without losing its structural integrity. Additionally, tungsten is used in these devices because it facilitates contact ionization when paired with certain vapours, such as cesium, which helps neutralize the space-charge effect that otherwise limits current density.123

While tungsten has a relatively high work function of 4.5 electron volts, its exceptional high-temperature strength and electrical conductivity make it a standard choice for demanding electronic applications and electrodes.324