Synthesis, structural, optical and dielectric properties of transition metal doped ZnMnO nanoparticles by sol-gel combustion technique

Abstract Nanocrystalline samples of Zn 0.94 Mn 0.06 O and transition metal ( TM ) doped Zn 0.94 Mn 0.01 TM 0.05 O ( TM  = Co, Ni, and Cu) were prepared by sol-gel auto combustion method. X-ray diffraction (XRD) pattern infers that all synthesized samples except Zn 0.94 Mn 0.01 Ni 0.05 O and Zn 0.94 Mn 0.01 Cu 0.05 O with secondary phases of NiO and CuO are in single phase with hexagonal wurtzite structure ( P 6 3 mc space group). Raman spectroscopy reveals four vibrational phonon modes are centered at 331, 380, 410, and 438 cm −1 , assigned as E 2 (H)-E 2 (L), A 1 (TO), E 1 (TO), and E 1 (LO) modes, respectively. A Raman spectrum of Zn 0.94 Mn 0.01 TM 0.05 O is entirely different from undoped Zn 0.94 Mn 0.06 O sample. Also, the infrared spectrum of transition metal doped samples is completely different from undoped Zn 0.94 Mn 0.06 O. Similar spectra are observed for Zn 0.94 Mn 0.01 Co 0.05 O, Zn 0.94 Mn 0.01 NiO, Zn 0.94 Mn 0.01 Cu 0.05 O and Zn 0.94 Mn 0.01 Zn 0.05 O samples. It was found that the band gap of Zn 0.94 Mn 0.06 O increased from 3.19 to 3.25eV by doping 5% transition metal oxide. Improved dielectric constant and reduced dielectric loss is measured for Zn 0.94 Mn 0.01 Ni/Cu 0.05 O as compared to Zn 0.94 Mn 0.06 O.