IntroductionCeramic envelopes for low wattage metal halide lamps were first introduced in the 3000K color temperature. The use of ceramic material created an opportunity for a breakthrough in low-wattage metal halide lamp technol ogy, resulting in improved color quality and efficacy. For decades, metal halide lamps have used envelopes of fused quartz, with either straight bodies or formed bod ies. The quartz material properties, however, limit the operating temperature range and therefore limit the design freedom to improve the color quality and main tenance of the low wattage metal halide lamp, while still obtaining good commercial life results.Metal halide salts provide the spectral power distribu tion to obtain the desired color temperature, color ren dering and luminous efficacy. After the successful com bination of the ceramic envelope technology with the standard low wattage 3000K. chemical formulation, a new application was found in the low-wattage 4000K color temperature range. The most critical design parameter is the operating temperature of the discharge tube. The higher the temperature, the better the color rendering, and the smaller the lamp-to-lamp color spread.The material properties of the ceramic discharge tube, as well as the manufacturing techniques employed, are important to ensure that also the low wattage 4000K metal halide lamp has an optimal performance with respect to luminous efficacy, maintenance, lifetime and color quality.

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