Luminous container for high voltage discharge lamp and method for mfg. multi-crystal transparent alumina sintered body
A high-pressure discharge lamp, polycrystalline transparent technology, applied in the manufacture of discharge tubes/lamps, components of gas discharge lamps, discharge lamps, etc., can solve problems such as arc suppression, loss of particle uniformity, and inability to control crystal particles
Inactive Publication Date: 2003-09-24
NGK INSULATORS LTD
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Problems solved by technology
[0006] However, in the prior art mentioned above, once the amount of MgO added is increased, it will form a solid solution with alumina and form oxygen lattice defects at the grain boundaries, which will cause blackening.
In addition, MgO has strong water absorption, and there will be defects such as hydrogen in the water entering the container will extinguish the discharge arc, and oxygen will promote the oxidation of the electrode.
[0007] Conversely, if the amount of MgO added is small, the effect as a sintering aid will not be exerted, crystal particles will not be controlled, particle uniformity will be lost, and light transmission will decrease due to low strength and incomplete discharge of air bubbles in the particles. And other issues
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[0015] Preferred embodiments of the present invention will be described in detail. The polycrystalline transparent alumina sintered body according to the present invention is produced through the following steps.
[0016] First, to high-purity alumina powder of 99.9% or more, add a sintering aid dissolved in pure water with a predetermined amount of carbonate or nitrate so that MgO is 0.0005 to 0.015% by weight, La 2 o 3 0.0025 to 0.025% by weight, while MgO and La 2 o 3 The total amount is not more than 0.030% by weight, and they are mixed with a ball mill for more than 10 hours.
[0017] Then, the mixture taken out from the ball mill is dried and calcined temporarily at 900-1200° C. for 2-5 hours. In this step, the additive is changed from a salt to an oxide.
[0018] After temporary firing, add binder and dispersant, mix with ball mill, remove air bubbles, and shape by casting method. get e.g. figure 1 Luminescent vessels for high-pressure discharge lamps of the shap...
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The method for producing a polycrystalline transparent alumina sintered body which is optimal in the type and amount of the sintering aid and is suitable for the light-emitting container of the high-pressure discharge lamp. Add 0.002 to 0.010% by weight of MgO and 0.005 to 0.020% by weight of La2O3 to alumina powder with a purity of 99.9% or more, and the total of MgO and La2O3 is 0.030% by weight or less, and 0.2≤MgO / La2O3≤0.5, and Mixing is performed, and the calcined alumina is temporarily calcined at 900-1200° C., and the calcined alumina is cast into shape. After the molded body is subjected to chelate treatment, it is fired under normal pressure at a maximum temperature of 1650-1900° C. for at least 1 hour in a reducing atmosphere.
Description
technical field [0001] The present invention relates to a light-emitting container for high-pressure discharge lamps used in high-pressure discharge lamps such as high-pressure sodium lamps and metal halide lamps, and a method for manufacturing a polycrystalline transparent alumina sintered body suitable for the light-emitting container. In particular, it relates to a method for producing a polycrystalline transparent alumina sintered body suitable for adding the optimum type and amount of sintering aid to alumina and suitable for light-emitting vessels of high-pressure discharge lamps. Background technique [0002] Polycrystalline transparent alumina sintered bodies are widely used as light-emitting containers for high-pressure discharge lamps such as high-pressure sodium lamps and metal halide lamps due to their good light transmission, heat resistance, and corrosion resistance. [0003] In order to make these polycrystalline transparent alumina sintered bodies have good l...
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IPC IPC(8): C04B35/115H01J9/24H01J61/30
CPCC04B35/115H01J9/247H01J61/302
Inventor 浅野修
Owner NGK INSULATORS LTD