Abstract: A spark plug comprising: a first electrode including a tip containing 1r as a main material, and a base member to which the tip is joined; and a second electrode opposed to the tip with a spark gap therebetween. The number of crystal grains appearing in a range of 0.25 mm2 on an arbitrary cross-section of the tip in a first direction connecting the tip and the second electrode within the spark gap, is not less than 20. When a length of each of the crystal grains in the first direction is denoted by Y, and a length of each of the crystal grains in a second direction perpendicular to the first direction is denoted by X, 5 ?m?X?100 ?m and Y/X?1.5 are satisfied.

Abstract: A spark plug comprising: a first electrode including a tip containing Ir as a main material, and a base member to which the tip is joined; and a second electrode opposed to the tip with a spark gap therebetween. The number of crystal grains appearing in a range of 0.25 mm2 on an arbitrary cross-section of the tip in a first direction connecting the tip and the second electrode within the spark gap, is not less than 20. When a length of each of the crystal grains in the first direction is denoted by Y, and a length of each of the crystal grains in a second direction perpendicular to the first direction is denoted by X, 5 ?m?X?100 ?m and Y/X?1.5 are satisfied.

Abstract: A spark plug having a tip provided on at least one of a center electrode and a ground electrode. The tip includes a body portion, a coating layer, and a high specific resistance layer. The body portion contains mostly Ir. The high specific resistance layer is provided on a side peripheral surface of the body portion, has a Ni content greater than the Ni content of the body portion and less than 50 mass %, and has a thickness of 2 ?m or greater and 45 ?m or less. The coating layer is provided on a side peripheral surface of the high specific resistance layer, contains 50 mass % or more of Ni, and has a thickness of 3 ?m or greater and 20 ?m or less. The tip has a specific resistance of 20×10?8 ?m or less at room temperature.

Abstract: A spark plug having a tip provided on at least one of a center electrode and a ground electrode. The tip includes a body portion, a coating layer, and a high specific resistance layer. The body portion contains mostly Ir. The high specific resistance layer is provided on a side peripheral surface of the body portion, has a Ni content greater than the Ni content of the body portion and less than 50 mass %, and has a thickness of 2 ?m or greater and 45 ?m or less. The coating layer is provided on a side peripheral surface of the high specific resistance layer, contains 50 mass % or more of Ni, and has a thickness of 3 ?m or greater and 20 ?m or less. The tip has a specific resistance of 20×10?8 ?m or less at room temperature.

Abstract: At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa?Sb corresponds to 35% or more of Sa.

Abstract: At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa?Sb corresponds to 35% or more of Sa.