Van der waals approximation for potassium bubbles in tungsten

Abstract

The finely dispersed potassium bubbles are responsible for the high-temperature sag resistance of lamp filaments; thus, the understanding of development of bubble structure is of practical importance. Usually, the ideal gas theory is used for describing the potassium bubbles in tungsten. Instead, we used the van der Waals approximation which can account for phase changes and describes a two-phase coexistence region. It is shown theoretically that bubbles in the practically important size range (some tenth of microns) can exist in a two-phase state. Some experimental findings are also better explained by the real gas approximation.