| 摘要 |
A spark plug including an insulator containing not less than 92 mass % and not greater than 96 mass % of Al component in terms of oxide, wherein the insulator is formed from an alumina sintered body comprising alumina crystal and a grain boundary phase present between crystal grains of the alumina crystal. Assuming that mass contents of an Si component, an Mg component, a Ba component, and a Ca component in terms of oxide are represented by MSiO2, MMgO, MBaO, and MCaO, respectively, and a sum of MSiO2, MMgO, MBaO, and MCaO is represented by Mt, the grain boundary phase contains these components so as to satisfy conditions (1) to (4) as follows: (1) 0.17≦MSiO2/Mt≦0.47; (2) 0.005≦MMgO/Mt≦0.07; (3) 0.29≦MBaO/Mt≦0.77; (4) 0.03≦MCaO/Mt≦0.19. |
| 主权项 |
1. A spark plug including an insulator containing not less than 92 mass % and not greater than 96 mass % of Al component in terms of oxide, wherein
the insulator is formed from an alumina sintered body comprising an alumina crystal and a grain boundary phase present between crystal grains of the alumina crystal, and assuming that mass contents of Si component, Mg component, Ba component, and Ca component in terms of oxide are represented by MSiO2, MMgO, MBaO, and MCaO, respectively, and a sum of MSiO2, MMgO, MBaO, and MCaO is represented by Mt, the grain boundary phase contains the Si component, the Mg component, the Ba component, and the Ca component so as to satisfy conditions (1) to (4) as follows:
0.17≦MSiO2/Mt≦0.47 (1)0.005≦MMgO/Mt≦0.07 (2)0.29≦MBaO/Mt≦0.77 (3)0.03≦MCaO/Mt≦0.19 (4) |
