Is it possible for a material to be a conductor in one direction and insulator in another?

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Main Question or Discussion Point

Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes up with temperature increases is metal, while resistances goes down is insulator, or semiconductor. If one finds that a material in x direction looks like metal in this resistance experimental, while in y no, is this situation possible? If so, could we say this material is metal just in x direction?
 

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  • #2
berkeman
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Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes up with temperature increases is metal, while resistances goes down is insulator, or semiconductor. If one finds that a material in x direction looks like metal in this resistance experimental, while in y no, is this situation possible? If so, could we say this material is metal just in x direction?
We use such material in laminated core transformers. The metal laminations are separated by non-conducting varnish. This is used to limit eddy current losses in the core:

https://qph.fs.quoracdn.net/main-qimg-99d6364e32355e6c00ab138131eeb3c5

main-qimg-99d6364e32355e6c00ab138131eeb3c5.gif
 

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  • #3
ZapperZ
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Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes up with temperature increases is metal, while resistances goes down is insulator, or semiconductor. If one finds that a material in x direction looks like metal in this resistance experimental, while in y no, is this situation possible? If so, could we say this material is metal just in x direction?
The cuprate superconductors are made up of layers of different atoms and molecules.

HTS_crystal_structures.jpg


Along the so-called [a,b] plane where the Cu-O planes lie, it is very conducting, almost like a typical metal. Along the c-axis (vertical direction), the resistivity can be several orders of magnitude higher, and often considered to be insulating.

There are many layered materials that behave this way, so it isn't that exotic anymore.

Zz.
 

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  • #4
fluidistic
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As far as I know graphite is such a material. Its resistivity is much higher in the c direction than in the a-b plane. I do not know about its metallicity though.
 
  • #5
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Thanks for your answers!
I know that there is anisotropy in many materials, what I want to know is when temperature goes up, resistance in x increases, while y no, is it usual?
 

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