SYNTHESIS AND CHARACTERIZATION (STRUCTURAL, OPTICAL AND MAGNETIC) OF UNDOPED AND DOPED ZnO-BASED NANOSTRUCTURED MATERIALS

Abstract

Pristine, La-doped and La-Fe co-doped ZnO powders were synthesized using the sol-gel co precipitation method. The pure and doped ZnO powders were characterized by XRD, FT-IR, XPS, FESEM, TEM, DRS, and VSM for the study of structural, optical, and magnetic properties. XRD of the samples show hexagonal wurtzite ZnO phase common to all with characteristic Bragg’s diffraction planes of (100), (002), (101), (102), (110), (103), (200), (112), (201), (004) and (202). Additional La2O2CO2 phase or La2O3 phase are identified for the La-doped ZnO samples heated at 400°C or 800°C respectively. At the same time, XRD analysis of La-Fe co-doped ZnO samples shows Fe3(CO)12 phase in addition to ZnO. The average particle size and elemental composition of the prepared samples were determined from FE SEM and EDX. The particles size of the 2 at. % La-doped sample is found to be the largest (49.51 nm), due to nanorod formation. For the lower dopant concentration (2.5 at. % La and 2.5at % Fe) in co-doped ZnO samples, microwave pre-treated followed by thermal heating at 400 0C, shows the rod like feature having an average particle size around 45.81 nm, which is the highest among all co-doped samples. The bandgap values of the samples range between 3.05 and 3.12 eV, having a quantum confinement effect, as revealed by DRS analysis. All the samples show feeble ferromagnetic properties at room temperature which range between 0.17 and 0.55 emu/gm. Among them, 5 at. % La and 5 at. % Fe co-doped ZnO sample shows the highest magnetization value of 0.55 emu/gm. The SQUID analysis of the samples reveals magnetic anisotropy increases on Fe doping which is good for spintronics applications of the materials. Additionally, ZnO rod morphology is expected to be enhanced for further spintronic effect.