Electrical and Thermal Conductivity

AUGUST 2017 ISSUE #104 TECHNICALTIDBITS MATERION PERFORMANCE ALLOYS

CURRENT EVENTS: ELECTRICAL AND THERMAL CONDUCTIVITY

By definition,electrical conductivity is a measure of how many free electrons are available to flow through the how well electrical current (charge in motion) can pass metal. (Free electrons are typically unpaired valence Like two peas in a through a material under the influence of an applied electrons.) In conductive metals, they are only loosely metallic pod. – How voltage/electric field.Thermal conductivity measures associated with the atomic nucleus, and are free to move how well heat (thermal energy in motion) can pass around in the metal. Metals atoms can be thought of as electrical and thermal through a material under a temperature differential. islands in a sea of shared free electrons. The electrical and conductivity are related thermal conductivities of a metal therefore depend on both In metals, both electric current (flow of charge) and heat the number of free electrons, as well as how tightly coupled in copper alloys. transfer (flow of thermal energy) are primarily carried by they are to the nucleus. electrons. The conductivities of metals therefore depend on

H He Li Be Metals and Non-Metals B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Electrical Fr Ra Ac Th Pa U Np Pu Am Cm Bk CF Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Ng Fl Mc Lv Ts Og H He Conductivity 18.4 43.1 Room Temperature Electrical Conductivity of Metals (%IACS) 0.27 C N O F Ne 36.1 38.6 66 0 P S Cl Ar 24 49.6 3.07 4.11 6.63 13 0.9 17.6 27.6 25.2 103 28.3 11.5 0 6.63 Se Br Kr Thermal 13.4 13.1 2.89 4.1 13.2 34 9.32 22.7 38.2 16 108 25 20.5 15.2 4.66 Te I Xe 8.62 5.35 2.8 2.08 2.46 2.68 2.3 1.83 1.92 1.32 1.5 1.86 2.12 2 2.55 6.9 2.96 5.21 13 32.5 9.3 18.2 36.6 16.3 73.4 1.8 11.5 8.35 1.64 4.31 At Rn Conductivity Fr Ra Ac 11 11.5 5.75 Np 1.3 Am Cm Bk CF Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Ng Fl Mc Lv Ts Og

H He Free Electrons 44 210 Room Temperature Thermal Conductivity of Metals (W/m K) 27.4 C N O F Ne 131 156 247 156 P S Cl Ar 108 201 15.8 11.4 31 67 7.79 80.4 69 82.9 398 113 40.6 60 50.2 Se Br Kr Wiedemann-Franz 58.2 35.4 17.2 21.1 52.3 142 50.2 117 150 70 428 97 83.7 62.8 25.9 6 I Xe 35.9 18.4 13.4 11.3 12.5 16.5 13.3 13.3 13.9 10.5 11.1 10.7 16.2 14.5 16.9 38.5 16.4 23 54.4 160 71.2 87.6 147 71.1 318 8.21 47 34 8.2 20 1.7 Rn Law Fr Ra Ac 77 47 27.6 Np 6.5 Am Cm Bk CF Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Ng Fl Mc Lv Ts Og Phonon Waves Figure 1. Electrical and Thermal Conductivities of Pure Metals. The displayed conductivity values are color-coded according to their relative magnitude. Note that electrical and thermal Phonon conductivities have the same relative magnitude, except for the metalloid elements near the boundary between the metals and non-metals. In the non-metals, electrons have little mobility, and heat is transferred by other mechanisms. These elements have widely varying thermal conductivities depending on form and structure, so there is no single value to put in the charts above. [Sources: ASM Handbook Vol. 2 and Wikipedia]

As shown in Figure 1, the highest conductivities are Form of Carbon Electrical Conductivity Thermal Conductivity found in the transition metals. Electron mobility, Graphite 0.22 % IACS 119 - 165 W/m K crystalline structure and physical state (solid or liquid, Diamond ~ 0% IACS 900 - 2300 W/m K single phase or multiple phases) all play a role in Carbon Nanotubes 1-20 % IACS > 3000 W/m K determining what the conductivities are. In the metals, electron mobility dominates thermal and electrical of conductivity, which can differ by an order of magnitude conductivity. If the electrical conductivity is high, then the depending on the atomic arrangement. Note also that while thermal conductivity will be high as well. In non-metals, diamond is a virtually perfect electrical insulator, its thermal The next issue of Technical Tidbits heat is conducted by other methods, and electrical conductivity is greater than that of any metal. Further note will discuss defining the maximum conductivity is virtually nonexistent. that carbon nanotubes have decent electrical conductivity, operating temperature of a material. indicating greater electron mobility in that crystalline form In the non-metals, crystalline structure becomes more than in graphite or diamond form, despite having the same important in determining thermal conductivity. For electron configuration. example, compounds of pure carbon have varying degrees ©2017 Materion Brush Inc. MATERION PERFORMANCE ALLOYS CURRENT EVENTS: ELECTRICAL AND THERMAL CONDUCTIVITY (CONTINUED) The electrical and thermal conductivities of metals You can easily see the Wiedemann-Franz relationship are related by what is known as the Wiedemann- in the color coding of the periodic tables in Figure 1. Franz Law, which can be stated as λ=(L∙T )/ρ, where So, if it holds for pure metals, does it hold for alloys Written by Mike Gedeon of Materion λ is the thermal conductivity (in Watts/m K), T is as well? The answer is yes, even though there are Performance Alloys Marketing the absolute temperature (in K), L is the Lorenz other elements present in the copper alloy matrix. Department. Mr. Gedeon’s primary focus is on electronic strip for the Constant (2.45x10-8 Volt2/K2), and ρ is the electrical Since the alloying elements disrupt the mobility of the automotive, telecom, and computer resistivity (in Ω•m). (Note that electrical resistivity is electrons, both electrical and thermal conductivities markets with emphasis on the inverse of the conductivity and yes, the units do are reduced by the same factor. You can see this application development. work out properly). clearly in Figure 2. References: “Properties of Pure Metals” ASM 450 Comparison of Copper Alloy Data Sheet Values 450 Comparison of Copper Alloy Data Sheet Values Handbook Vol.2 Properties and ) ) K K

300 Reported Thermal 300 ASM International y y t t i i Conductivity v v i i 250 250 t t c c Reported Thermal

u “Technical Tidbits” Issues 23, 24 u d d 200 Wiedemann-Franz 200 Conductivity n n o o Relationship 150

150 C C

Newey, Charles and Weaver, l l Wiedemann-Franz a a 100 100 Relationship m m Graham Materials Principles and r r e e 50 50 Practice ©1990 The Open T h T h 0 0 University 0.00E+00 1.00E-07 2.00E-07 3.00E-07 4.00E-07 0 20 40 60 80 100 120 Reported Electrical Resistivity (ohm-m) Reported Electrical Conductivity (% IACS) Please contact your local sales representative for further Figure 2. Electrical and Thermal Conductivity as Reported on Various Data Sheets. information or questions There is only minor variation from the Wiedemann-Franz relationship. The left chart shows the relationship between the pertaining to Materion or variables as presented in the equation. The right chart shows that in copper alloys, there is a linear relationship between our products. thermal and electrical conductivity.

Health and Safety Handling copper beryllium in solid So, if electrons are not the primary conductor everything else in physics, are quantized, which form poses no special health risk. of heat in non-metals, then what is? Temperature means that they only exist in discrete multiples of the Like many industrial materials, is a measure of the average kinetic energy of base state. In this case, a quantized vibrational wave beryllium-containing materials the vibrations of the individual atoms in the is called a phonon. Thermal energy is transferred may pose a health risk if crystalline lattice. back and forth between the electrons and the recommended safe handling moving phonons. In non-metals, the thermal energy moves through practices are not followed. the material as a wave of vibration. These waves are Phonon waves can pass more easily through some Inhalation of airborne beryllium may cause a serious lung disorder elastic waves, and behave similarly to sound waves atomic arrangements than through others. This is why in susceptible individuals. The moving through a material. Such waves are called thermal conductivity of non-metals will vary greatly Occupational Safety and Health phonon waves. (In fact, a sound wave is essentially a depending on the crystalline structure. Administration (OSHA) has set low frequency phonon wave). These waves, like most mandatory limits on occupational respiratory exposures. Read and follow the guidance in the Material Safety Data Sheet (MSDS) before working with this material. For additional information on safe handling practices or technical data on copper beryllium, contact Materion Performance Alloys or your local representative. TECHNICALTIDBITS Materion Performance Alloys Sales 6070 Parkland Blvd. +1.216.383.6800 Mayfield Heights, OH 44124 800.321.2076 [email protected] Technical Service +1.216.692.3108 800.375.4205 [email protected]