Microstructure and Optical Properties of Co x Zn 1– x Ga 2 O 4 (0 ≤ x ≤ 1) Nanoparticles

Co x Zn 1– x Ga 2 O 4 (0 ≤ x ≤ 1) nanoparticles were synthesized by the sol‐gel method and characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), 71 Ga solid‐state NMR spectroscopy, and UV/Vis spectroscopy. The results show that the Co x Zn 1– x Ga 2 O 4 nanoparticles were successfully obtained when the annealing temperature was 500 °C or above. The crystallite size of the as‐prepared particles was 20–55 nm, and increased with increasing annealing temperature and decreasing x value. Zn 2+ and Ga 3+ ions were located in both the tetrahedral and octahedral sites in Co x Zn 1– x Ga 2 O 4 nanoparticles, and the inversion parameter (two times the fraction of Ga 3+ ions in tetrahedral sites) decreased with increasing annealing temperature and increased with cobalt enrichment. The absorption spectra indicate that Co 2+ ions are located in the tetrahedral sites as well as in the octahedral sites in the nanoparticles. The fraction of octahedral Co 2+ ions decreased with increasing annealing temperature.