Abstract
Recent investigations about electron emission materials for HID lamps are reviewed. In high pressure mercury and high pressure sodium lamps, new emission materials like Ba1.8Sr0.2CaWO6 have been developed and resulted in a significant improvement of lamp performance. In the case of metal halide lamps, rare-earth oxides have been used because of their higher stability in lamp performance. However, the performance of metal halide lamps is still poor, and thus much work on the improvement is continued.
