| 摘要 |
A spark plug 100 has a glaze layer 2d formed on a surface of an alumina based insulator 2 contains 1 mol % or less of a Pb component in terms of PbO. The glaze layer 2d comprises 35 to 55 mol % of a Si component in terms of SiO2; 15 to 35 mol % of a B component in terms of B2O3; 5 to 20 mol % of a Zn component in terms of ZnO; 0.5 to 20 mol % of a Ba component in terms of BaO; and 10 to 15 mol % in total of at least one alkaline metal component of Na, K and Li, in terms of Na2O, K2O and Li2O, respectively.
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