We have investigated the isothermal phase diagram of the GaRuCu ternary system at 1073 K by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy to determine whether the stable icosahedral quasicrystal (i-phase) forms, as it does in the similar AlRuCu system, and new intermetallic phases exist. This is the first systematic investigation of the GaRuCu system. No stable i-phase is identified in the GaRuCu alloy system. However, we found a new ternary (¸) phase in the GaRuCu system, which is characterized as a C-centered orthorhombic lattice with a¸ = 11.80 ¡, b¸ = 6.04 ¡, and c¸ = 3.07 ¡. The (ideal) chemical composition of the ¸-phase is Ga50Ru37.5Cu12.5 (Ga4Ru3Cu). This new phase is stable up to 1073 K. Above 1173 K, the ¸-phase transforms to the cubic GaRu (¢) phase without any secondary phases. Thus, there is an orderdisorder transition between the low-temperature ¸-phase and the high-temperature cubic ¢-phase in this temperature range.
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