US Patent 12027826 Spark plug

A spark plug having a firing pad with minimal silicon diffusion and limited silicon oxidation at grain boundaries that can cause undesirable vertical cracking. In one embodiment, the firing pad has a multilayer structure having a base layer and a firing layer, wherein the base layer is a non-precious metal based material having silicon, and wherein the firing layer is a precious metal based material having yttrium in an amount of 0.1 to 0.5 wt %, inclusive. After at least 190 hours of isothermal treatment of at least 1000° C., an extent of vertical cracking from the sparking surface does not exceed 50% of a thickness of the firing pad or the firing layer.