| 摘要 |
The ceramic consists essentially of Al2O3. It can be used as a support, in particular for a heating conductor, and as an external coating. It is electrochemically stable, in other words is not affected when subjected to a heating voltage, even prolonged, at temperatures in excess of 600<o>. This ceramic has a very low alkali content, less than 0.2 per cent by weight of Na2O and K2O. Advantageous machining and in particular pressing features are obtained when the ceramic contains between 2.5 and 10 per cent barium- or strontium silicate as the flux, whereby the total content of Na2O, K2O, CaO and MgO is less than 1 per cent by weight and the molar ratio of BaO or SrO : SiO2 is between 2:1 and 1:12.5. Such a ceramic with a ratio of BaO : SiO2 of 2.6:1 parts by weight is electrochemically stable to approximately 1400<o>C and at 1300<o>C has a bending strength which is still in the region of 300 N/mm<2>. |
