| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug having a glazed layer with lower content for Pb component and moreover which is superior in mechanical strength, especially superior in impact resistance. SOLUTION: For the spark plug 100 containing a resistor, the glazed layer 2d formed on a surface of insulator 2 of alumina series in made to have content of Pb component to be 1 mol% or less when converted into PbO, and contains Si component, B component, Zn component, Al component, and Ba and/or Sr component, and the content of F component is 1 mol% or less. Furthermore, it contains one kind or at least two kinds of alkaline metal components, in which Li is an essential component and contains one kind or at least two kinds of ions of phosphate ions, sulfate ions, fluoride ions and chloride ions in a range of 0.5 to 10 mol%, and where Vickers hardness Hv is 100 or higher.
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