Optical properties of α‐ and β‐CuZn brasses in the region of quantum absorption

The optical constants n and k of CuZn brasses with Zn content of 39, 40, 41, 47, 50 at% (β‐phase) and 35 at% (α‐phase) are measured at 293 K, and with Zn content of 35, 39, and 50 at% at 78 K also, in the 1 to 0.25 μm spectral range by the polarimetric method. From n and k reflectance R(λ), high‐frequency conductivity σ(ω) (where ω is the light wave cyclic frequency), the real and imaginary parts ε1(ω) and ε2(ω) of the complex dielectric constant, and the electron characteristic loss function ε/ε + ε are derived. Their concentration and temperature dependences are analyzed. The different characters of the concentration and temperature dependences of the absorption edge of α‐ and β‐brasses confirm that its origin in these alloys is not the same: in α‐brasses the edge is formed by interband transitions from EF to vacant states of the conduction band, while in β‐brasses by d‐band to EF transitions. No substantial change in the optical interband absorption is observed in both, the concentration and temperature (martensitie) b.c.c. to f.c.c. transitions.