Abstract: One aspect relates to an apparatus includes a ceramic body including a first surface and a further surface. The first surface is opposite the further surface, the first surface includes a first opening. The further surface includes a further opening. The first opening and the further opening are connected by a tunnel, which at least partly includes a tunnel filling and is occluded by the tunnel filling. The tunnel filling includes a first constituent, including a cermet, and a second constituent. The first and second constituents are electroconductingly connected to one another. The first constituent has a first electrical conductivity and the second constituent has a second electrical conductivity, which differs from the first by at least 5·10?4 Siemens per meter (S/m). The ceramic body is characterized by a further electrical conductivity. The first electrical conductivity is more by at least 1·105 Siemens per meter (S/m) than the 15 further electrical conductivity.

Abstract: One aspect relates to an apparatus comprising a ceramic body including a first surface and a further surface. The first surface is opposite the further surface, the first surface includes a first opening. The further surface includes a further opening. The first opening and the further opening are connected by a tunnel, which at least partly includes a tunnel filling and is occluded by the tunnel filling. The tunnel filling includes a first constituent, including a cermet, and a second constituent. The first and second constituents are electroconductingly connected to one another. The first constituent has a first electrical conductivity and the second constituent has a second electrical conductivity, which differs from the first by at least 5·104 S/m. The ceramic body is characterized by a further electrical conductivity. The first electrical conductivity is more by at least 1·105 S/m than the further electrical conductivity.