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I need a part or material for a planned experiment (the experiment is similar to those described in my articles http://arxiv.org/abs/1208.0066 and http://arxiv.org/abs/1109.1626 ). The problem is that the required resistivity (about 0.3 Ohm-cm or of the same order of magnitude) is much higher than that of metals and much lower than that of dielectrics. Eventually, I need a long cylindrical part, about 1.5 mm diameter and about 1 m length. So far I have considered semiconductors, conducting polymers, and absorbing materials of http://www.eccosorb.com/Collateral/Documents/English-US/Electrical%20Parameters/ls%20parameters.pdf . The latter materials seem good, but they are essentially foams, and the required part cannot be machined from them. As for semiconductors and conductive polymers, I don't have a clear idea how to get (to order) a material with the required resistivity and how to make (to order) the required part. I need the above resistivity at a frequency of about 25 GHz, so, in principle, I could use a nonconductive, but absorbing (at the required frequency) material, but I would prefer a material that is conducting for direct current as well, to be able to measure the absorbed power. I would prefer a material with decent mechanical properties, so that I could, e.g., strain (tighten) the cylindrical part.

Any advice?

EDIT (02/02/2014): I have finally obtained the required parts. They are made of doped polysilicon. I am grateful for the answers.

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2 Answers

up vote 1 down vote accepted

This is a good challenge!

Here is maybe a solution: Ordering a 1 meter long Si rod with the correct doping level. It seems they are already able to make 2 mm diameter rods of 1 meter long out of pure silicon. (http://www.goodfellow.com/catalogue/GFCat4J.php?ewd_token=5IQzQHXALuzqcQFMm0Hg7C5opN6zxs&n=O76P2NzWunxfCV3bOzRYzd6IvAfLFt)

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Thank you very much, this is probably a useful reference. I will have to find out about doping. –  akhmeteli Jul 9 '13 at 4:01
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Maybe you can create a joint/junction and vary the pressure across the pads. Resistance is inversely proportional to pressure so you can fine tune your experiment by simply turning screws.

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I am afraid I don't understand the geometry. Could you give some reference? What materials are supposed to be joined - dielectrics, metals, something else? And I need a material with homogeneous resistivity, not just some integral resistance. –  akhmeteli Jul 9 '13 at 4:04
    
@akhmeteli Sorry I do not know enough about electricity to answer your questions. All I know is that interface resistance depends on contact pressure. –  ja72 Jul 9 '13 at 12:51
    
I am afraid I need homogeneous resistivity, not just resistance at some interface. Thank you anyway. –  akhmeteli Jul 16 '13 at 12:05
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