Vacuum circuit breaker

A vacuum circuit breaker comprising a vacuum interrupter accommodated in a casing filled with insulating gas, the vacuum interrupter comprising:

• a vacuum container having an insulating tube and seal members for sealing both ends of the insulating tube;
• and
• a pair of contacts arranged in the vacuum container and configured to be contactable with or separable away from each other, and being fixed to conductive shaft members,
• wherein at least one of the contacts comprises an electrode material containing a Cu phase and a phase of solid solution particles uniformly dispersed in the Cu phase, the solid solution particles comprising a solid solution of Cr and a heat resistant element selected from Mo, W, Ta, Nb, V, and Zr;
• wherein the electrode material comprises 20 to 70% by weight of Cu, 1.5 to 64% by weight of Cr, and 6 to 76% by weight of the heat resistant element, relative to a weight of the electrode material, with the balance being unavoidable impurities;
• and
• wherein the solid solution particles contained in the electrode material have an average particle size of 20 μm or smaller, and are uniformly dispersed in the Cu phase with a dispersion state index of 1.0 or lower.