Structural, optical and photoluminescence studies of heavily Mn-doped ZnO nanoparticles annealed under Ar atmosphere

Undoped and heavily Mn-doped with ZnO nanoparticles (Zn_1?xMn_xO, x?=?0.0, 0.05, 0.1 and 0.2) annealed under Ar atmosphere have been synthesized by a sol–gel method. The structural properties and optical absorption of the prepared samples have been examined by powder X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared (FTIR) spectroscopy and UV–visible spectrophotometer. Hexagonal wurtzite structure of the samples is confirmed by the XRD spectra. The average crystalline size of the Zn_1?xMn_xO nanoparticles has been calculated from X-ray line broadening and is decreased from 35.73 to 18.24?nm with increase in Mn concentrations from 0.0 to 0.2. The increase in lattice parameters indicates the substitution of Mn in ZnO lattice. SEM and TEM photographs indicated that the grain size of undoped ZnO is bigger than the Mn-doped ZnO which is due to the limitations of grain growth upon Mn doping. The presence of functional groups and the chemical bonding due to Mn doping is confirmed by FTIR spectra. PL spectra of the Zn_1?xMn_xO system showed that the shift in near band edge emission at 390?nm and a blue band emission at 450–490?nm which confirms the substitution of Mn.