Contact material for a vacuum interrupter

A contact material for a vacuum interrupter comprising:

• (a) from 25 to 65% by volume of a highly conductive component selected from the group consisting of Ag, Cu and combinations thereof;
• (b) no more than 1% by volume of an auxiliary component selected from the group consisting of Fe, Co, Ni and combinations thereof;
• and
• (c) a remaining percentage by volume of an arc-proof component comprising a carbide of an element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and combinations thereof;
• wherein
• (A) the composition of the contact material is such a composition that the percentage of Ag based on the total amount of the highly conductive component is from 40 to 100% by volume,
• (B) the texture of said contact material is such a texture that
• (i) a portion or all of said contact material comprises a matrix composed of the highly conductive component and a skeleton composed of the arc-proof component having a grain size from 0.3 to 3 micrometers and a remaining portion of said contact material comprises only the highly conductive component which forms a coarse island-shaped texture having a grain size of at least 5 micrometers, and
• (ii) the average grain distance of said arc-proof component in portions except said island-shaped texture portion calculated by equation (1):
• ##EQU3## (where .lambda..sub.wc is the average grain distance of wc (.mu.m), d.sub.wc is the grain size of WC (.lambda.m), f.sub.i is % by volume of portions except the island-shaped texture, and f.sub.wc is % by volume of WC) is from 0.1 to 1 micrometers;
• and
• (C) the relative density of said contact material is at least 90% by volume.