| 摘要 |
PURPOSE:To enable the elimination of increased number of holes from a ceramic material by successively firing a ceramic material in an oxygen atmosphere and an oxygen-free atmosphere at a low temperature and a high temperature. CONSTITUTION:A formed ceramic material 14 is fired for a prescribed time at a temperature lower than a prescribed firing temperature in a firing furnace while introducing oxygen as an atmospheric gas into the space between two alumina crucibles 10, 12 through an atmosphere-introducing pipe 18. Nitrogen is introduced in place of oxygen and the material is fired for a prescribed time. After finishing the firing process, the temperature of the firing furnace is raised to a prescribed firing temperature, the ceramic material is fired in oxygen atmosphere for a prescribed time, the atmosphere is changed to nitrogen and the firing is carried out for a prescribed time. When the firing process is finished, oxygen is introduced again into the furnace to oxidize the surface of the formed material 14. An increased number of holes can be eliminated from the formed ceramic material 14 by this process compared with conventional process. |
