| 摘要 |
PROBLEM TO BE SOLVED: To produce a semiconductive ceramic capable of being inexpensively produced in a large amount by simplifying a production process by including alumina crystal grains and one ore more kinds of crystal grins of MnNb2 O6 , MnAlO4 and MnFe2 O4 and regulating a volume specific resistance to be at a specific value. SOLUTION: This semiconductive ceramic comprises 40-85 vol.% alumina crystal grains, and one or more kinds of crystal grains of MnNb2 O6 , MnAlO4 and MnFe2 O4 , and has 10<4> -10<12> Ω.cm volume specific resistance and >=10 kV/mm absolute breakdown voltage. The ceramic is obtained by mixing an alumina powder with one or more kinds of powders of manganese oxide, niobium oxide and iron oxide in prescribed proportions, compacting the obtained raw material by a press molding or the like to form a prescribed shape, and firing the obtained compact in atmospheric surrounding at 1,200-1,350 deg.C. In the production process, components such as SiO2 , MgO, CaO, Na2 O, ArO2 and Ta2 O5 which do not take part in the crystal phase are contaminated as impurities, but the total of the contaminated amounts is required so as to be regulated to be <=0.1 wt.%. |
