Method for doping polycrystalline alumina ceramics

Abstract

The invention discloses a method of doping in polycrystal alumina ceramics, including the following steps: the alumina product is formed first and is initially burnt under the temperature of 900 DEG C to 1,250 DEG C for one or two hours; then the burnt alumina product is put together with the impurity but the two do not contact directly, and then are heated to 800 -1,500 DEG C for two hours to five hours, thereby ensuring that impurity is heated and changed into steam which is evenly distributed on an alumina product; last, the alumina product with the impurity is heated for a third time to 1,700 to 2,000 DEG C for 10 hours to 12 hours. The invention adopting steam doping can keep the distribution of impurities more even, in particular suitable for the doping of impurity in small quantity. The invention has the advantages of mechanical production, fast speed and large yield, etc. in comparison with prior slurry blending doping patterns.

Description

technical field [0001] The invention relates to a method for manufacturing ceramics, in particular to a method for adding a small amount of auxiliary materials to polycrystalline alumina ceramics. Background technique [0002] In high intensity discharge lamps, translucent polycrystalline alumina (PCA) is used as the arc tube material. The production process of PCA includes the following basic steps: mixing, molding and pre-densification, and solid-state sintering. Among them, the mixing is to add additives, binders and other chemicals that are beneficial to molding, such as dispersants, defoamers, lubricants, etc. We mostly use high-purity ultra-fine alumina powder as raw material, add appropriate amount of rare earth compound, and add water ball to grind into slurry to complete the mixing. In the production of ceramic discharge tubes, in order to obtain more uniform grains, magnesium oxide should be added to the alumina powder. Because there is metal halide in the disch...

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Problems solved by technology

Because there is metal halide in the discharge tube of the ceramic metal halide lamp, and it will react with magnesium oxide, affecting the life of the lamp, light effect, etc., so the amount should be added as little as possible. When we add impurities less than At 250PPM, it is difficult to mix them evenly with the above method, and the firing effect often does not meet the predetermined requirements.

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