| 摘要 |
<p>Sintered polycrystalline alumina body, esp. a tube, made of equiaxed Al2O3 grains with uniform size contains is not >150 ppm. MgO with no porosity nor sec. phase, so the tube has improved light transmission (LT) including improved linear LT (LLT). With a test piece 0.75 mm thick, the total LT is pref. >=93% over the entire visible spectrum. The outer surface of the tube is pref. polished without etching the grain boundaries, to improve the LLT. The alumina pref. has average grain size 26 mu m with range 20-35 mu m. The tube is pref. used in an improved high performance electric discharge lamp where electrode coated with an emission material are fitted i the ends of the tube. The tube is pref. pressed from a mixt. of high purity alumina of uniform grain size with not >0.1% MgO, to obtain >=30% theoretical density, followed by sintering in vacuo or H2 at 1700-1950 degrees C. Alternatively, binder and lubricant can be added to the mixt. and the pressing presintered at 950-1200 degrees C. in O2. The total LT of the lamp is increased, e.g. from 92.3% to 93.5%.</p> |
