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Pure silver (also called fine silver) exhibits the highest electrical and thermal conductivity of all metals. It is also resistant against oxidation. Major disadvantages are its low mechanical wear resistance, the low softening temperature, and especially its strong affinity to sulfur and sulfur compounds. In the presence of sulfur and sulfur containing compounds brownish to black silver sulfide layer are formed on its surface. These can cause increased contact resistance or even total failure of a switching device if they are not mechanically, electrically, or thermally destroyed. Other weaknesses of silver contacts are the tendency to weld under the influence of over-currents and the low resistance against material transfer when switching DC loads. In humid environments and under the influence of an electrical field silver can creep (silver migration) and cause electrical shorting between adjacent current paths.
Semi-finished silver materials can easily be warm or cold formed and can be clad to the usual base materials (<xr id="fig:Strain hardening of Ag bei cold working"/> and <xr id="fig:Softening of Ag after annealing after different degrees"/>). For attachment of silver to contact carrier materials welding of wire or profile cut-offs and brazing are most widely applied. Besides these mechanical processes such as wire insertion (wire staking) and the riveting (staking) of solid or composite contact rivets are used in the manufacture of contact components.
====Fine-Grain Silver====
Fine-Grain silver is defined as a silver alloy with an addition of 0.15 wt% of nickel. Silver and nickel are not soluble in each other in solid form. In liquid silver, only a small amount of nickel is soluble as the phase diagram illustrates (<xr id="fig:Phase diagram of silver nickel"/><!--(Fig. 2.51)-->) illustrates. During solidification of the melt, this nickel addition gets finely dispersed in the silver matrix and eliminates the pronounce coarse grain growth after prolonged influence of elevated temperatures (<xr id="fig:Coarse grain micro structure of Ag"/><!--(Fig. 2.49)--> and <xr id="fig:Fine grain microstructure of AgNiO"/><!--(Fig. 2.50)-->).
<div class="multiple-images">
AgPd alloys are hard, arc erosion resistant, and have a lower tendency towards material transfer under DC loads (<xr id="tab:Contact and Switching Properties of Silver-Palladium Alloys"/>)<!--(Table 2.19)-->. On the other hand, the electrical conductivity is decreased at higher Pd contents. The ternary alloy AgPd30Cu5 has an even higher hardness, which makes it suitable for use in sliding contact systems.
AgPd alloys are mostly used in relays for the switching of medium to higher loads (> 60V, > 2A) as shown in (<xr id="tab:Application Examples and Forms of Suppl for Silver-Palladium Alloys"/><!--(Table 2.20)-->). Because of the high palladium price, these formerly solid contacts have been widely replaced by multi-layer designs such as AgNi0.15 or AgNi10 with a thin Au surface layer. A broader field of application for AgPd alloys remains in the wear resistant sliding contact systems.
!Silver Content<br />[wt%]
!Additives
!Theoretical<br />Density<br />[g/cm<sup>3</sup>]!Electrical<br />Resistivity<br />[μΩ·cm]!colspan="2" style="text-align:center"|Electrical<br />Conductivity<br />[% IACS] [MS/m]!Vickers<br />Hardness<br />Hv1[HV0,1]
!Tensile<br />Strength<br />[MPa]
!Elongation<br />(soft annealed)<br />A[%]min.
!Manufacturing<br />Process
!Form ofSupply|-|Ag/SnO<sub>2<br /sub>Supply98/2 SPW|97 - 99|WO<sub>3</sub>|10,4|59 ± 2|57 ± 15|215|35|Powder Metallurgy|1
|-
|Ag/SnO<sub>2</sub> 92/8PW10<br />8 SPW
|91 - 93
|WO<sub>3</sub>
|10,1
|51 ± 2
|62 ± 15
|255
|25
|Powder Metallurgy
|1
|-
|Ag/SnO<sub>2</sub> 90/10 SPW
|89 - 91
|WO<sub>3</sub>
|10
|47 ± 5
|
|250
|25
|Powder Metallurgy
|1
|-
|Ag/SnO<sub>2</sub> 88/12 SPW
|87 - 89
|WO<sub>3</sub>
|9.9
|246 ± 5|8667 ± 15|50270|50 - 95|200 - 320|3020|Powder Metallurgy<br />
|1
|-
|Ag/SnO<sub>2</sub> 9092/8 SPW4|91 - 93|WO<sub>3</sub>|10,1|51 ± 2|62 ± 15|255|25|Powder Metallurgy|1,2|-|Ag/10PW10SnO<sub>2<br /sub>90/10 SPW4
|89 - 91
|WO<sub>3</sub>
|10
|
|
|
|
|Powder Metallurgy
|1,2
|-
|Ag/SnO<sub>2</sub> 88/12 SPW4<br />
|87 - 89
|WO<sub>3</sub>
|9,8
|46 ± 5
|80 ± 10
|
|
|Powder Metallurgy
|1,2
|-
|Ag/SnO<sub>2</sub> 88/12 SPW6
|87 - 89
|MoO<sub>3</sub>
|9.8
|42 ± 5|70 ± 10|||Powder Metallurgy|2.08|83-|48Ag/SnO<sub>2</sub> 97/3 SPW7|55 96 - 10098|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>|||||220 |Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 90/10 SPW7|89 - 33091|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>|9,9||||28
|Powder Metallurgy
|12
|-
|Ag/SnO<sub>2</sub> 88/12PW10<br />12 SPW7
|87 - 89
|Bi<sub>2</sub>O<sub>3</sub> and WO<sub>3</sub>|9.78|42 ± 5|70 ± 10|||Powder Metallurgy|2|-|Ag/SnO<sub>2</sub> 98/2 PMT1|97 - 99|Bi<sub>2</sub>O<sub>3</sub> and CuO|10,4|57 ± 2.17|79|46215|35|Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 96/4 PMT1|95 - 97|Bi<sub>2</sub>O<sub>3</sub> and CuO||||||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 94/6 PMT1|93 - 95|Bi<sub>2</sub>O<sub>3</sub> and CuO||||||Powder Metallurgy|1,2|-|Ag/SnO<sub>2</sub> 92/8 PMT1|91 - 93|Bi<sub>2</sub>O<sub>3</sub> and CuO|10|50 ± 2|62 ± 15|240|25|Powder Metallurgy|1,2|60 - 106|230 Ag/SnO<sub>2</sub> 90/10 PMT1|89 - 33091|Bi<sub>2</sub>O<sub>3</sub> and CuO|10|48 ± 2|65 ± 15|240
|25
|Powder Metallurgy
|1,2|-|Ag/SnO<sub>2</sub> 88/12 PMT1|87 - 89|Bi<sub>2</sub>O<sub>3</sub> and CuO|9,9|46 ± 5||260|20|Powder Metallurgy|1,2
|-
|Ag/SnO<sub>2</sub> 90/10PE<br />10 PE
|89 - 91
|Bi<sub>2</sub>O<sub>3</sub> and CuO
|9.,8|48 ± 2.04|84|49
|55 - 100
|230 - 330
|1
|-
|Ag/SnO<sub>2</sub> 88/12PE<br />12 PE
|87 - 89
|Bi<sub>2</sub>O<sub>3</sub> and CuO
|9.,7|2.17|79|46± 5
|60 - 106
|235 - 330
|1
|-
|Ag/SnO<sub>2</sub> 88/12 TOS F<br />PMT2
|87 - 89
|In<sub>2</sub>O<sub>3</sub>CuO|9.8|2.22|78,9|45|100 - 12090 ± 10|330 -430|25|Inernal OxidationPowder Metallurgy
|1,2
|-
|Ag/SnO<sub>2</sub> 9086/10WPD<br />14 PMT3|89 85 - 9187|AgBi<sub>2</sub>MoOO<sub>43</sub>and CuO|9.9|2.13,8|81|47|70 - 12095 ± 10
|
|
|2
|-
|Ag/SnO<sub>2</sub> 8894/12WPD<br />6 LC1|87 93 - 8995|AgBi<sub>2</sub>O<sub>3</sub> and In<sub>2</sub>MoOO<sub>43</sub>|9.,8|2.27|76|4445 ± 5|75 - 12055 ± 10
|
|
|Powder Metallurgy
|2
|-
|Ag/SnO<sub>2</sub> 90/10 POX1
|89 - 91
|In<sub>2</sub>O<sub>3</sub>
|9,9
|50 ± 5
|85 ± 15
|310
|25
|Internal Oxidation
|1,2
|-
|Ag/SnO<sub>2</sub> 90/10 POX1
|87 - 89
|In<sub>2</sub>O<sub>3</sub>
|9,8
|48 ± 5
|90 ± 15
|325
|25
|Internal Oxidation
|1,2
|-
|Ag/SnO<sub>2</sub> 90/10 POX1
|85 - 87
|In<sub>2</sub>O<sub>3</sub>
|9,6
|45 ± 5
|95 ± 15
|330
|20
|Internal Oxidation
|1,2
|-
|}
</figtable>
<figure id="fig:Micro structure of Ag ZnO 92 8 PW25">
[[File:Micro structure of Ag ZnO 92 8 Pw25.jpg|left|thumb|<caption>Micro structure of Ag/ZnO 92/8 Pw25PW25: a) perpendicular to extrusion direction b) parallel to extrusion direction</caption>]]
</figure>
|40 - 60
|-
|AgC DF<br />GRAPHOR DF*)[[#text-reference1|<sup>1</sup>]]
|95.7 - 96.7
|8.7 - 8.9
|69 - 76
|40 - 44
|-
|}
<div id="text-reference1"><sub>1</sub> Graphite content 3.8 wt%, Graphite particles and fibers parallel to switching surface</div>
</figtable>
<caption>'''<!--Table 2.34:-->Application Examples and Forms of Supply of Silver– Graphite Contact Materials'''</caption>
<table class="twocolortable">
<tr><th><p class="s12">Material</p><p class="s12"></p></th><th><p class="s12">Application Examples</p></th><th><p class="s12">Form of Supply</p></th></tr><td><p class="s12">Ag/C 98/2</p><p class="s12"></p></td><td><p class="s12">Motor circuit breakers, paired with Ag/Ni</p></td><td><p class="s12">Contact tips, brazed and welded contact parts, some contact rivets </p><p class="s12">Contact profiles (weld tapes), Contact tips, brazed and welded contact parts</p></td></tr><tr><td><p class="s12">Ag/C 97/3</p><p class="s12"></p><p class="s12">Ag/C 96/4</p><p class="s12"></p><p class="s12">Ag/C 95/5</p><p class="s12"></p><p class="s12">Ag/C DF</p></td><td><p class="s12">Circuit breakers, paired with Cu, Motor-protective circuit breakers, paired with Ag/Ni,</p><p class="s12">Fault current circuit breakers, paired with Ag/Ni, Ag/W, Ag/WC, Ag/SnO<sub>2</sub><span class="s45"></span>, Ag/ZnO,</p><p class="s12">(Main) Power switches, paired with Ag/Ni, Ag/W</p></td><td><p class="s12">Contact tips, brazed and welded contact</p><p class="s12">parts, some contact rivets with</p><p class="s12">Ag/C97/3</p></td/></tr></table>
</figtable>
