Amalgams for fluorescent lamps Part II: The systems Bi-Pb-Hg and Bi-Pb-Au-Hg

摘要

In nowadays compact fluorescent lamps, having coolest spot temperatures in the range 60-130 deg C, arnalgams based on the eutectic Bi-In and Bi-Pb-Sn alloys are used to control the mercury vapour pressure inside the lamp. The consequence of the trend towards smaller and more attractive compact fluorescent lamps is that the amalgam temperature increases. In this paper the materials and thermodynamic properties of the amalgams Bi-Pb-Hg and Bi-Pb-Au-Hg are described. The mercury vapour pressure measurements show that these amalgams can be used for controlling the optimal mercury vapour pressure inside fluorescent lamps at temperatures in the range 60-150 deg C. In the ternary Bi-Pb-Au system the new ternary compound BiPb_3Au has been found for which the crystal structure and melting point have been determined. The results of XRD, EPMA, DTA and mercury vapour pressure measurements are combined to formulate a thermodynamic model for the mercury activity in both liquid and solid Bi-Pb-Hg and Bi-Pb-Au-Hg.