Niobium-ceramic feedthrough assembly and ductility-preserving sealing process

A process for fabricating a niobium-ceramic through-wall assembly for a ceramic or metal wall of a vessel, comprising the steps of:

• firing at a temperature of about 1400.degree.-2000.degree. C. in a pure inert atmosphere or vacuum a niobium-ceramic through-wall assembly comprising an alumina or yttria sealing means having a bore therethrough, and a ductile niobium throughpiece close fitted to and extending through the bore;
• wherein the throughpiece consists essentially of about 0-2 weight % zirconium, remainder pure niobium;
• the sealing means before firing is sufficiently below full density to shrink fit during firing to form a hermetic seal between the throughpiece and the sealing means;
• the pure inert atmosphere or vacuum includes less than about 5 ppm oxygen and less than about 5 ppm hydrogen;
• the pure inert atmosphere is flowing at about 4 liters/minute;
• and the firing is carried out for a time sufficient to form the hermetic seal;
• and
• cooling the assembly to below about 250.degree. C. while maintaining the pure inert atmosphere or vacuum.

A process for fabricating a niobium-ceramic electrical feedthrough assembly for a lamp having an alumina, yttria, or sapphire lamp envelope, comprising the steps of:

• firing at a temperature of about 1400.degree.-2000.degree. C. in a pure inert atmosphere or vacuum a niobium-ceramic feedthrough assembly comprising an alumina or yttria end seal having a bore therethrough, and a ductile niobium tube close fitted to and extending through the bore;
• wherein the niobium tube consists essentially of about 0-2 weight % zirconium, remainder pure niobium;
• the end seal before firing is sufficiently below full density to shrink fit during firing to form a hermetic seal between the niobium tube and the end seal;
• the pure inert atmosphere or vacuum includes less than about 5 ppm oxygen and less than about 5 ppm hydrogen;
• and the firing is carried out for a time sufficient to form the hermetic seal;
• and
• cooling the assembly to below about 250.degree. C. while maintaining the pure inert atmosphere or vacuum.

A process for fabricating a niobium-ceramic electrical feedthrough assembly for a lamp having an alumina, yttria, or sapphire lamp envelope, comprising the steps of:

• firing at a temperature of about 1400.degree.-2000.degree. C. in a pure inert atmosphere or vacuum a niobium-ceramic feedthrough assembly comprising an alumina or yttria end seal having a bore therethrough, and a ductile niobium tube close fitted to and extending through the bore;
• wherein the niobium tube consists essentially of about 0-2 weight % zirconium, remainder pure niobium;
• the end seal before firing is sufficiently below full density to shrink fit during firing to form a hermetic seal between the niobium tube and the end seal;
• the pure inert atmosphere or vacuum includes less than about 5 ppm oxygen and less than about 5 ppm hydrogen;
• the pure inert atmosphere is flowing at about 4 liters/minute;
• and the firing is carried out for a time sufficient to form the hermetic seal;
• and
• cooling the assembly to below about 250.degree. C. while maintaining the pure inert atmosphere or vacuum.

A process for fabricating a lamp having an alumina, yttria, or sapphire lamp envelope, comprising the steps of:

• close fitting an end seal to an open end of a lamp envelope formed from alumina, yttria, or sapphire;
• wherein the end seal has an axial bore therethrough and is formed from alumina or yttria having a similar thermal expansion coefficient to that of the lamp envelope;
• heating the close fitted lamp envelope and end seal at a temperature and for a time sufficient to form a first hermetic seal between the lamp envelope and end seal;
• positioning a ductile niobium feedthrough tube to extend through the axial bore through the heated end seal to form a lamp envelope, end seal, and niobium tube combination;
• wherein the niobium tube consists essentially of about 0-2 weight % zirconium, remainder niobium;
• and the axial bore is of a size to permit close fitting of the niobium tube therethrough;
• firing at a temperature of about 1400.degree.-2000.degree. C. in a pure inert atmosphere or vacuum the lamp envelope, end seal, and niobium tube combination;
• wherein the end seal after heating and before firing is sufficiently below full density to shrink fit during firing to form a second hermetic seal between the end seal and the niobium tube;
• the pure inert atmosphere or vacuum includes less than about 5 ppm oxygen and less than about 5 ppm hydrogen;
• and the firing is carried out for a time sufficient to form the second hermetic seal;
• and
• cooling the fired lamp envelope, end seal, and niobium tube combination to below about 250.degree. C. while maintaining the pure inert atmosphere or vacuum.