| 摘要 |
PROBLEM TO BE SOLVED: To enhance the dielectric strength, insulating property and mechanical strength of an alumina-base insulator while reducing the number of closed pores and voids by incorporating a specified amount of an Sn component into the insulator. SOLUTION: An Sn component is incorporated into an insulator by 0.05-2.0 wt.% (expressed in terms of SnO). The insulator contains 85-98 wt.% (expressed in terms of Al2O3) Al component, may contain 0.07-0.5 wt.% (expressed in terms of Na2O) Na component and preferably contains 0.1-15 wt.% (expressed in terms of oxides), in total, of one or more additive elements selected from Si, Ca, Mg, Ba, Zn and B. The average number of voids of >=10 μm size per 1 mm2 observed in the cross-sectional texture of the insulator is <=100 and >=35 kV/mm dielectric strength at 20 deg.C is ensured. |
