THE FORMATION OF A ZIRCONATE PHASE WITHIN THE EMISSION MIX FOR LOW-PRESSURE HG-AR DISCHARGE LAMPS

It was discovered in the early 1950s that vaporization of barium from the cathode in a fluorescent lamp can be reduced tremendously with the addition of zirconium oxide to the coating mix. The lamp industry has been using this added material (Zr or ZrO2) since then. However, the reason for this improvement is poorly understood. In this paper, it is shown by using x-ray diffraction that a barium-strontium zirconate ph ase forms under conditions that mimic different lamp operating charact eristics. The formation of this compound may be related to the observe d improvements in lamp properties.