A feed-through element for harsh environments is provided that includes a support body with at least one access opening, in which at least one functional element is arranged in an electrically insulating fixing material. The electrically insulating fixing material contains a glass or a glass ceramic with a volume resistivity of greater than 1.010.sup.10 cm at the temperature of 350 C. The glass or a glass ceramic has a defined composition range in the system SiO.sub.2B.sub.2O.sub.3-MO.

A feed-through element for harsh environments is provided that includes a support body with at least one access opening, in which at least one functional element is arranged in an electrically insulating fixing material. The electrically insulating fixing material contains a glass or a glass ceramic with a volume resistivity of greater than 1.010.sup.10 cm at the temperature of 350 C. The glass or a glass ceramic has a defined composition range in the system SiO.sub.2B.sub.2O.sub.3-MO.

A feed-through element for harsh environments is provided that includes a support body with at least one access opening, in which at least one functional element is arranged in an electrically insulating fixing material. The electrically insulating fixing material contains a glass or a glass ceramic with a volume resistivity of greater than 1.010.sup.10 cm at the temperature of 350 C. The glass or a glass ceramic has a defined composition range in the system SiO.sub.2B.sub.2O.sub.3-MO.

A join is provided that includes a first joining partner, a second joining partner having a surface, an electrically insulating component connecting the first joining partner in the second joining partner so that the first joining partner is electrically insulated from the second joining partner and so that the first joining partner extends from the surface. The electrically insulating component has a structure between the first and second joining partners that elongates from the surface along the first joining partner. The electrically insulating component and/or the structure is an at least partially crystallized glass.

An electrical feedthrough includes: a main body having a through-opening running through the main body and comprising titanium or titanium alloy; an insulation material accommodated in the through-opening, the insulation material comprising a glass; and an electrical conductor that extends through the insulation material accommodated in the through-opening. The glass is a lanthanum borate glass comprising the following components (in mol % based on oxide): 22.0-37.0 B.sub.2O.sub.3; 1.0-12.0 La.sub.2O.sub.3; 10.5-23.0 SiO.sub.2; 29.0-45.0 RO (MgO+CaO+SrO); 0.1-6.0 Nb.sub.2O.sub.5+ZrO.sub.2+TiO.sub.2+Ta.sub.2O.sub.5; and greater than 3.00 SiO.sub.2/(Nb.sub.2O.sub.5+ZrO.sub.2+TiO.sub.2+Ta.sub.2O.sub.5). The glass, on determination of hydrolytic stability in accordance with DIN ISO 720:2021-12, has an Na.sub.2O equivalence value of <1250 g/g. The feedthrough has long-term autoclaving stability and an insulation resistance of the feedthrough after 300 autoclaving operations is at least 1*10.sup.9 ohms.