A hermetic feedthrough for an implantable medical device includes a sheet having a hole defined therethrough, wherein the sheet comprises a first material that is an electrically insulative ceramic comprising alumina. The feedthrough further includes a second material substantially filling the hole so as to form a conduit, the second material having platinum and an additive that includes alumina. The second material does not include SiO2, MgO, or CaO. The first and second materials have a co-fired bond therebetween, the co-fired bond hermetically sealing the hole.
