Influence of Bi Doping Concentrations on the Structural, Morphological, Dielectric, Optical and Magnetic Properties of ZnO Nanoparticles

Herein, we report the improved dielectric behaviour of zinc oxide (ZnO) nanoparticles through the incorporation of various bismuth (Bi) ion doping concentrations (Zn1-xBixO; x = 0, 0.0025, 0.0050, 0.0075 and 0.01). X-ray diffraction (XRD) analysis confirms that no secondary or impurity phase was detected in pristine ZnO nanoparticles, whereas a small amount of beta-Bi2O3 phase was identified as an additional peak for higher x = 0.0075 and 0.01 Bi doping concentrations. Fourier transform infrared (FTIR) spectra were recorded to analyze the effect of Bi doping on the vibrational frequencies of ZnO nanoparticles. Scanning electron microscopy (SEM) investigation revealed that the surface morphology of ZnO nanoparticles is significantly modified by Bi doping. Energy-dispersive spectroscopy (EDS) measurement confirmed the presence of Bi element in Bi-doped ZnO (BZO) nanoparticles. The optical absorption measurement indicates that the absorption band edge of ZnO nanoparticles is slightly blue-shifted, from 3.38 to 3.48 eV, by Bi ion incorporation. Dielectric measurement reveals that the dielectric constant is considerably enhanced by adding various Bi ion doping concentrations and temperatures, whereas it decreases with increasing frequency. The result of the vibrating sample magnetometer measurement shows that maximum coercivity (633.69 Oe) and retentivity (8.42 emu/g) values were observed for x = 0.0050 Bi doping concentrations.