Material needed for 3000K+ use

Tungsten 3695K melting point

Tungsten would probably be a decent choice.

This is just a nutty idea.. but how about a gallium filled ceramic boat, surface heated by very high frequency inductance? The reason I suggest this silly idea is because gallium has the lowest vapor pressure of all pure elements and it's boiling point is insainly high...

whats a nernst lamp?

-Scott

I gather 3000K is its limit, above that it vapourises too fast. I need something significantly hotter.

NT

Why so hot? If you want output, use more surface area (longer or broader filament). If you need the color, maybe filtering a yellower lamp would be easier.

I'll look that up.

Its a ceramic rod, preheat it with a gas flame until it conducts, then apply power directly through it. It needs no glass bulb or vacuum, as the ceramic is chemically stable at operating temp. The higher the temp, the more it conducts, so its thermally unstable.

thanks, NT

I'll look that up.

Its a ceramic rod, preheat it with a gas flame until it conducts, then apply power directly through it. It needs no glass bulb or vacuum, as the ceramic is chemically stable at operating temp. The higher the temp, the more it conducts, so its thermally unstable.

thanks, NT

I remember reading one day that SiC becomes more electrically conductive with temperature.

-Scott

Sorry, when I suggested Tungsten I thought you were talking about a Nernst Lamp which in microscopy is just a filament wide enough to cover the field of view - tungsten ribbons work well for that.

If you need a cylindrical glower stable in air you might consider a Thorium Oxide cylinder (MP about 3300C, the highest melting point for oxides; it may be your only choice). Cermet.com supplies Thoria. Thoria has a Fluorite structure so it'll likely be a fast oxygen ion conductor when it is hot.

However, rather than rely on that it might be prudent to just run a tungsten filament down its axis; solder/seal the wire inside the tube with silver or gold & water cool the ends so the metals don't melt or react. Sounds like a fun project.

Dave

thanks for another idea to follow :)

NT