Electrical Resistivity and Conductivity - Resistivity of Various Materials

Resistivity of Various Materials

  • A conductor such as a metal has high conductivity and a low resistivity.
  • An insulator like glass has low conductivity and a high resistivity.
  • The conductivity of a semiconductor is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or specific frequencies of light, and, most important, with temperature and composition of the semiconductor material.

The degree of doping in semiconductors makes a large difference in conductivity. To a point, more doping leads to higher conductivity. The conductivity of a solution of water is highly dependent on its concentration of dissolved salts, and other chemical species that ionize in the solution. Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, relative to the conductivity of pure water at 25 °C. An EC meter is normally used to measure conductivity in a solution. A rough summary is as follows:

Material Resistivity
ρ (Ω•m)
Superconductors 0
Metals 10−8
Semiconductors variable
Electrolytes variable
Insulators 1016

This table shows the resistivity, conductivity and temperature coefficient of various materials at 20 °C (68 °F)

Material ρ (Ω•m) at 20 °C σ (S/m) at 20 °C Temperature
coefficient
(K−1)
Reference
Silver 1.59×10−8 6.30×107 0.0038
Copper 1.68×10−8 5.96×107 0.0039
Annealed copper 1.72×10−8 5.80×107
Gold 2.44×10−8 4.10×107 0.0034
Aluminium 2.82×10−8 3.5×107 0.0039
Calcium 3.36×10−8 2.98×107 0.0041
Tungsten 5.60×10−8 1.79×107 0.0045
Zinc 5.90×10−8 1.69×107 0.0037
Nickel 6.99×10−8 1.43×107 0.006
Lithium 9.28×10−8 1.08×107 0.006
Iron 1.0×10−7 1.00×107 0.005
Platinum 1.06×10−7 9.43×106 0.00392
Tin 1.09×10−7 9.17×106 0.0045
Carbon steel (1010) 1.43×10−7 6.99×106
Lead 2.2×10−7 4.55×106 0.0039
Titanium 4.20×10−7 2.38×106 X
Grain oriented electrical steel 4.60×10−7 2.17×106
Manganin 4.82×10−7 2.07×106 0.000002
Constantan 4.9×10−7 2.04×106 0.000008
Stainless steel 6.9×10−7 1.45×106
Mercury 9.8×10−7 1.02×106 0.0009
Nichrome 1.10×10−6 9.09×105 0.0004
GaAs 5×10−7 to 10×10−3 5×10−8 to 103
Carbon (amorphous) 5×10−4 to 8×10−4 1.25 to 2×103 −0.0005
Carbon (graphite) 2.5e×10−6 to 5.0×10−6 //basal plane
3.0×10−3 ⊥basal plane
2 to 3×105 //basal plane
3.3×102 ⊥basal plane
Carbon (diamond) 1×1012 ~10−13
Germanium 4.6×10−1 2.17 −0.048
Sea water 2×10−1 4.8
Drinking water 2×101 to 2×103 5×10−4 to 5×10−2
Silicon 6.40×102 1.56×10−3 −0.075
Deionized water 1.8×105 5.5×10−6
Glass 10×1010 to 10×1014 10−11 to 10−15 ?
Hard rubber 1×1013 10−14 ?
Sulfur 1×1015 10−16 ?
Air 1.3×1016 to 3.3×1016 3×10−15 to 8×10−15
Paraffin 1×1017 10−18 ?
Fused quartz 7.5×1017 1.3×10−18 ?
PET 10×1020 10−21 ?
Teflon 10×1022 to 10×1024 10−25 to 10−23 ?

The effective temperature coefficient varies with temperature and purity level of the material. The 20 °C value is only an approximation when used at other temperatures. For example, the coefficient becomes lower at higher temperatures for copper, and the value 0.00427 is commonly specified at 0 °C.

The extremely low resistivity (high conductivity) of silver is characteristic of metals. George Gamow tidily summed up the nature of the metals' dealings with electrons in his science-popularizing book, One, Two, Three...Infinity (1947): "The metallic substances differ from all other materials by the fact that the outer shells of their atoms are bound rather loosely, and often let one of their electrons go free. Thus the interior of a metal is filled up with a large number of unattached electrons that travel aimlessly around like a crowd of displaced persons. When a metal wire is subjected to electric force applied on its opposite ends, these free electrons rush in the direction of the force, thus forming what we call an electric current." More technically, the free electron model gives a basic description of electron flow in metals.

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