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Conductor Bulk Resistivity & Skin Depths

Available bulk resistivity values (ρ) and relative permeability (μr)used to calculate skin depths (δσ) can vary considerably depending on the source. In fact, the values for permeabilities are so far-ranging that I hesitated to even include any of them in the table. The ones used here are typical, gathered from many of the links listed at the bottom of the page. Therefore, it is incumbent upon the user to determine his own value based on a trusted source. Even NIST[1] and CRC[2] do not fully agree on bulk resistivity values for materials as well-known as copper and aluminum. Most common conductors used in cabling have a relative permeability of very near unity (1).

Note that ferromagnetic materials often experience a falloff in relative permeability as frequency increases. For example least one investigator[3] has measured a value as low as 1 for nickel at 10 GHz.

Here is the equation for skin depth

Here is a skin depth calculator

Material Chemical

Formula

 Bulk

Resistivity

@20C

µΩ×cm

(Ω×10-8m)

 Relative

Permeability

μ/μ0

 Skin Depth

(µm@f)
1

MHz

 10

MHz

 100

MHz

 1

GHz

 10

GHz

 100

GHz
Aluminum Al 2.65 1 81.9 25.9 8.19 2.59 0.819 0.259
Beryllium Be 3.3 1 91.4 28.9 9.14 2.89 0.914 0.289
Brass Cu70/Zn30 7 1 133 42.1 13.3 4.21 1.33 0.421
Bronze Cu89/Sn11 15 1 195 61.6 19.5 6.16 1.95 0.616
Carbon C (graphite) 1375   1866 590 187 59.0 18.7 5.90
Cadmium Cd 7.3   136 43.0 13.6 4.30 1.36 0.430
Chromium Cr 13.2 1 183 57.8 18.3 5.78 1.83 0.578
Cobalt Co 6.34 600 5.8 1.6 0.52 0.16 0.052 0.016
Constantan Cu60Ni40 49   352 111 35.2 11.1 3.52 1.11
Copper Cu 1.69 1 65.4 20.7 6.54 2.07 0.654 0.207
Dural Al95/Cu 4/Mg 1 5   112.54 35.6 11.3 3.56 1.13 0.356
Gallium Ga 15.5   198 62.7 19.8 6.27 1.98 0.627
Gold Au 2.2 1 74.7 23.6 7.47 2.36 0.747 0.236
Graphite C 783.7   1409 446 141 44.6 14.1 4.46
Inconel alloy 600 Ni72/Cr16/Fe 8 103 1 511 162 51.1 16.2 5.11 1.62
Indium In 8.8   149 47.2 14.9 4.72 1.49 0.472
Iridium Ir 5.1   114 35.9 11.4 3.59 1.14 0.359
Iron Fe 10.1 500 7.2 2.3 0.72 0.23 0.072 0.023
Lead Pb 20.6 1 228 72.2 22.8 7.22 2.28 0.722
Lithium Li 9.29   153 48.5 15.3 4.85 1.53 0.485
Magnesium Mg 4.2 1 103 32.6 10.3 3.26 1.03 0.326
Mercury Hg 95.9 1 493 156 49.3 15.6 4.93 1.56
Molybdenum Mo 5.7 1 120 38.0 12.0 3.80 1.20 0.380
Monel alloy 400 Ni65/Cu33/Fe 2 49   352 111 35.2 11.1 3.52 1.11
mu-Metal   47 30,000 2.0 0.64 0.20 0.064 0.020 0.0064
Nickel Ni 6.9 200 9.3 3.0 0.93 0.30 0.093 0.030
Nichrome Ni80/Cr20 108   523 165 52.3 16.5 5.23 1.65
Palladium Pd 10.8 1 165 52.3 16.5 5.23 1.65 0.523
Platinum Pt 10.58 1 164 51.8 16.4 5.18 1.64 0.518
Potassium K 6.8   131 41.5 13.1 4.15 1.31 0.415
Rhodium Rh 4.7 1 109 34.5 10.9 3.45 1.09 0.345
Silver Ag 1.63 1 64.3 20.3 6.43 2.03 0.643 0.203
Sodium Na 4.9   111 35.2 11.1 3.52 1.11 0.352
Steel     100            
Tantalum Ta 13.5   185 58.5 18.5 5.85 1.85 0.585
Tantalum Nitride TaN 252   799 253 79.9 25.3 7.99 2.53
Tin (pure) Sn 12.6 1 179 56.5 17.9 5.65 1.79 0.565
Titanium Ti 54 1 370 117 37.0 11.7 3.70 1.17
Tungsten W 5.4 1 117 37.0 11.7 3.70 1.17 0.370
Urnaium U 27   262 82.7 26.2 8.27 2.62 0.827
Yttrium Y 53   366 116 36.6 11.6 3.66 1.16
Zinc Zn 5.96   123 38.9 12.3 3.89 1.23 0.389
Zirconium Zr 44   334 106 33.4 10.6 3.34 1.06

 1: National Institute of Standards and Technology

 2: Chemical Rubber Corporation

 3: Microwave Characterization of Nickel, Stepan Lucyszyn, Imperial College London (thanks to Reto Z. for pointing this out)

Related Pages on RF Cafe

- Coaxial Cable Specifications

- Capacitor Dielectrics & Descriptions

- Dielectric Constant, Strength, & Loss Tangent

- Conductor Bulk Resistivity & Skin Depths

- Coaxial Cable Equations

- Coaxial Cable Specifications

- Coaxial Cable Vendors

- Coaxial Resonator

- Skin Depth Calculator

- Coaxial Connector Usage Chart
Innovative Power Products Resistors Terminations
Copper Mountain Technologies (VNA) - RF Cafe
 everythingRF RF & Microwave Parts Database - RF Cafe
Windfreak Technologies Frequency Synthesizers - RF Cafe

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