Structural and magnetic properties of cadmium oxides with different annealing temperatures

A series of cadmium oxide samples (CdOs) were synthesized by thermal treatment method with various annealing temperatures (TA = 500 ℃ - 900 ℃). All samples crystallize in a pure cubic structure with Fm3̅m symmetry. The crystallite size, lattice parameter and volume change slightly with TA, and show an unexpected inflection point for the sample with TA = 800 ℃ (CdO-800), while the average particle size increases monotonically from ∼0.4 µm to ∼3.0 µm. Distinct ferromagnetic features accompanied by diamagnetic and/or paramagnetic phases were detected. The XPS data indicate the valence of cadmium and oxygen vacancy concentration varies with TA, which are responsible for the ferromagnetic origin in CdOs. CdO-800 shows the maximum magnetization, significant coercive force and residual magnetization. Oxygen vacancy plays a crucial role in the ferromagnetic performance, which can be effectively controlled by changing the sintering temperature. This work claims new characteristics for CdO besides optical and semi-conducting, which may be important in the preparation and possible applications for CdO dilute magnetic semiconductors. •The lattice parameter and grain size of CdO vary with annealing temperature.•The ferromagnetism of CdO stems from Cd and O vacancies.•This work claimed new characteristics for CdO besides optical and semi-conducting.