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 Si, Ba and a rare earth element. As to the insulator, in analysis with a scanning transmission electron microscope using an electron beam of 1 nm in probe diameter, the Si and rare earth element are detected at a crystal grain boundary of 15 nm or less in thickness, alkali-earth metals are under a detection limit at the crystal grain boundary, and a diffraction mottle is present in an electron beam diffraction pattern of a portion where the Ba is detected. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT