Patent ID: 8618725

Claim:
A spark plug comprising: a center electrode; a ground electrode provided so as to form a gap between the ground electrode and the center electrode; and a noble metal tip provided on at least one of the center electrode and the ground electrode, wherein, the noble metal tip contains Mp (Mp is an element group consisting of Pt or Pt and Pd, and the amount of Pd is 20 mass % or less with respect to the mass of the noble metal tip), Cu, and M (M is at least one element selected from the element group consisting of Rh, Ir, Ru, Re, and W) in a total amount of 95 mass % or more; and the proportions by mass of Mp, Cu, and M (Mp, Cu, M) in a Mp-Cu-M ternary composition diagram fall within a region defined by a line connecting point D (95, 5, 0), point E (94.5, 5, 0.5), point F (87, 5, 8), point G (80, 12, 8), point H (79.5, 20, 0.5), point I (80, 20, 0), and point D (95, 5, 0) in this order (the region including the line).