Phase transitions of Cu3+xSi observed by temperature-dependent x-ray powder diffraction

Abstract Phases in the system Cu 3+ x Si were analyzed by temperature-dependent x-ray powder diffraction and differential scanning calorimetry on samples with nominal composition Cu 74 Si 26 and Cu 78 Si 22 in the temperature range between 30 °C and 700 °C. Contrary to previous works, which report three phases in the system, we identified six distinct phases, labeled, in order of increasing temperature, η ‴ , η ″ , η ′ , η 3 , η 2 , η 1 . All these phases can be indexed with a similar basic unit cell. However, each phase has a different superstructure or modulation vectors.