Sm and Er partial alternatives of Co in Co3O4 nanoparticles: Probing the physical properties

In the attempt of producing multifunctional materials, the Sm3+ and Er3+ partial alternatives of Co in Co3O4 nanoparticles were synthesized via the co-precipitation method with the chemical formula Co3-2xSmxErxO4 (0.00 < x < 0.06). The structural analysis by XRD revealed that x = 0.02 at.% is the maximum solubility of Sm and Er in the Co3O4 matrix, which beyond it there are small traces of the Sm2O3 secondary phase. The size of the nanoparticles, obtained from XRD and TEM, decreased with increasing the co-doping percentages, leading to an increase in the surface area, and hence, benefit the magnetic recording density and electron transport efficiency. Moreover, the co-doping changed the morphology from slightly agglomerated spherical-shaped nanoparticles to the highly agglomerated mixed morphology of welded nanorods and nanokernels. The tetrahedral and octahedral functional groups were revealed by FTIR spectroscopy, declaring the successful formation of Co3O4 spinel structure. The UV?vis spectroscopy showed a monotonic decrease in the absorbance with increased codopants concentration accompanied by a widening of the band gap energy that serves photovoltaic materials, solar cells ... The defect concentrations were investigated by photoluminescence spectroscopy that assured the presence of cobalt interstitial as the main defect. The intensity is quenched with x = 0.01 at.%, addressing the heterogeneous photocatalysis, and enhanced to reach its maximum with x = 0.06 at.%, fostering the electrochemical supercapacitors. The concentration of these defects directly influences the magnetic behavior as proposed by the Bound Magnetic Polaron theory. The codopants render the nanoparticles softer magnetic materials due to the decrease in their coercivity and retentivity, which is good for data storage applications and electromagnetic materials.

Automated summary

By synthesizing Sm3+ and Er3+ partially substituted Co in Co3O4 nanoparticles via co-precipitation, the maximum solubility of dopants and the control of nanoparticle size were achieved, resulting in a change in morphology. Different co-doping concentrations influenced the optical, magnetic, and electrochemical properties of the materials.