To my knowledge, material doesn't matter when it comes to building destroyers, but quality does.
However, if I was to place a door for defense, I would probably only use an artifact one; I've noticed they take a lot longer to get past, and they won't be destroyed, only disassembled.
Bonus points if you can set it on fire, so that those stupid trolls/MBs/etc.
won't Will have !!FUN!! destroying it.
edit: damn, ninja'd. Oh well, I'll just use this opportunity to remind you all that while artifact doors are indestructible, they can still be uprooted from the ground.
While I'm at it,
You could force an artifact to be made out of certain materials ala Planepacked, but I have no idea how to specify anything else.
Oh, man, imagine getting a lignite weapon artifact. Set it on fire- bam, flaming sword. I don't think military would pick it up, though, but still.
The Deathgate succession game ended up with a flaming sword somehow, until it was accidentally atom-smashed, and everyone who touched it almost immediately ended up bleeding out because of their burns. IIRC, it killed at least a dozen haulers just to move it a few floors. Deathgate's labyrinthine design probably didn't help that much. Not even an adamantine-clad soldier could hold it for long, there was even a suggestion to mod in nether-cap armour at one point just to see if it was possible to pick it up.