SPARKPLUG

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PROBLEM TO BE SOLVED : To provide a sparkplug having an insulator which enables the enhancement of a voltage-endurance performance under a high-temperature environment. SOLUTION : A sparkplug comprises an insulator composed of an alumina-based sintered compact. The insulator includes 90-98 wt.% of an Al component in terms of oxide. The insulator includes 1-5 wt.% of Si components, 0.1-1 wt.% of Mg components, 2 wt.% or less of Ca components, 0.3-6 wt.% of Ba components, and 0.11-5 wt.% of rare earth components in terms of oxide. In analysis with a scanning transmission electron microscope using an electron beam of 1 nm in probe diameter, Si and a rare earth element are detected at a crystal grain boundary of 15 nm or less in thickness, and alkali-earth metals are under a detection limit at the crystal grain boundary. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT