Structural, optical and magnetic properties of ErxZn1-xO nanoparticles: The impact of the Er-content

Abstract

In this study we report on both the successful synthesis of ErxZn1-xO nanoparticles (x = 0.000, 0.005, 0.010, 0.030, 0.050, 0.075, and 0.100) and characterization (structural, optical, and magnetic) of the as-produced nanomaterials. The nanoparticles were produced by the polymeric precursor method (Pechini’s method). X-ray diffraction and Raman spectroscopy showed formation of hexagonal wurtzite phase in all samples. Meanwhile, only samples with a high Er-content (x = 0.075 and x = 0.100) exhibited a minority (up to 7 % w/w) secondary crystalline phase (Er2O3). The Rietveld refinement method was employed to assess details of the structural parameters. It was demonstrated that the increase of the Er-content leads to systematic mean crystalline size reduction (from ∼80 to ∼13 nm) and band gap shrinking (from ∼3.17 to ∼3.00 eV). The UV-Vis spectra showed the presence of characteristic Er3+-ion absorption bands. Likewise, emission peaks associated with Er3+-ion 4S3/2 → 4I15/2 electronic transition were verified by room temperature photoluminescence (PL). Strong differences in the PL spectra profiles of the ErxZn1-xO nanoparticles with respect to the PL spectrum of a reference Er2O3 sample, suggested that the majority of Er3+-ions replace Zn2+-ions in the wurtzite hosting matrix. Magnetic measurements show a paramagnetic behavior in all doped samples. The χ×T and M×Hcurves were successfully fitted to Curie-Weiss law and Brillouin modified model, showing the existence of short-range antiferromagnetic correlation.