Along with the motivation of enhancing conductivity of ZnO by Al doping, to further widen the useable wavelength range and improve the efficiency of ZnO-based devices, band-gap engineering by alloying is an accessible technique. Cadmium oxide (CdO) is also a II–VI SW033291 semiconductor with a narrower bandgap of 2.3 eV. The bandgap of ZnO could be red-shifted to blue or even green light spectra range by CdO alloying. Unfortunately, the phase segregation between wurtzite ZnO and rocksalt CdO in (Zn, Cd)O alloy is a major hinder for application. Moreover, the incorporation of Cd would introduce stress, and may enhance electron scattering and grain boundary barrier effects ,  and . Apparently, it is necessary to clarify the influence of Cd doping on the structural and optical properties of ZnO matrix. Meanwhile, because the effective ionic radius of Al3+ (0.39 Å, coordination number CN = 4) is smaller than that of Zn2+ (0.60 Å, CN = 4), while the effective ionic radius of Cd2+ (0.78 Å, CN = 4) is larger than that of Zn2+, the Al and Cd doping efficiency in ZnO matrix might be enhanced through the codoping way (with bigger Cd2+ and smaller Al3+, reducing the mismatch of doping elements and ZnO matrix). Nevertheless, the thorough study of narrowing band gap and phase segregation after Cd doping on the structural and optical properties of (Cd, Al)-codoped ZnO powders has been rarely reported.