Cation distribution and photoluminescence properties of Mn-doped ZnGa2O4 nanoparticles

• The distribution of cations in Mn-doped ZnGa2O4 nanoparticles was studied.
• All the cations occupy both the tetrahedral and octahedral sites of spinel structure.
• The inversion parameter increases with decreasing temperature and Mn-enrichment.
• The luminescence properties were also studied.

Mn-doped ZnGa2O4 nanoparticles with the composition of MnxZn1−xGa2O4 (0≤x≤1) were prepared by the citrate sol–gel method. The cation distribution in the nanoparticles was studied by using X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The results show that the nanoparticles with the size of 20–48 nm were obtained when the precursor was annealed at 600 °C or above, and the size increases with increasing annealing temperature. The cations (Ga3+, Zn2+ and Mn2+) occupy the tetrahedral (Td) sites as well as the octahedral (Oh) sites of spinel structure in the nanoparticles. Ga3+ ions are located in a large proportion at the octahedral sites and in a small proportion at the tetrahedral sites. The inversion parameter (two times the fraction of Ga3+ in the tetrahedral sites) increases with decreasing annealing temperature and Mn-enrichment. The luminescent properties were studied by using fluorescence spectrophotometer. The photoluminescence (PL) spectra exhibit green and red emissions with excitation wavelength of 304 nm, which is attributed to 4T1(4G)→6A1(6S) transition of Mn2+ ions in the tetrahedral and octahedral sites of MnxZn1−xGa2O4 nanoparticles, respectively.