Improvement of metal halide lamps by complex formation

The effective partial pressure of low volatile halides can be increased due to the formation of gaseous complexes. It has been found that this effect can be successfully applied in high pressure gas discharge lamps leading to an enhancement of the luminous efficacy and/or an improvement of the colour rendering properties. Some selection rules have been derived for combining suitable metal halides. Lamp experiments are reported for lamps with sodium halides and the halides of the alkaline earth group, the best results being obtained with aluminium halides as the complex forming partner.