Synthesis and physical properties of pure NiO and Ni_1-2xMg_xM_xO (M= Cu, Ru) nanoparticles: Role of growth temperature

Herein, low-cost chloride precursors, EDTA, and NaOH were employed through a facile coprecipitation synthesis route to prepare pure and codoped NiO nanoparticles: Ni1-2xMgxMxO, where M = Cu and Ru and x = 1, 4, and 8 at%. To examine the impact of reaction temperature on the thermal, structural, morphological, optical, and magnetic properties of the prepared samples, the precursor aqueous solutions were heated at 60, 70, and 80 C-degrees. Data analysis revealed the strong dependence of all the studied properties on reaction temperature and codoping. Thermogravimetric analysis (TGA) was performed to evaluate the thermal stability of the prepared samples. The face-centered cubic (fcc) crystallization of NiO was maintained at all the applied temperatures and doping concentrations. X-ray diffraction (XRD) patterns showed the good incorporation of Mg2+ and Cu2+ ions with the host Ni2+ ions in Ni1-2xMgxCuxO samples, while peaks of RuO(2 )appeared as an impurity phase in Ni1-2xMgxRuxO samples. Tiny spherical nanoparticles with a crystallite size of 6 nm were produced at 80 C-degrees and 8 at% (Mg, Ru) codoping. Energy dispersive X-ray (EDX) analysis confirmed that the elemental compositions of the synthesized samples were in stoichiometric ratios. The UV-Vis spectra demonstrated a monotonic increase in band gap with reaction temperature and codoping. The estimated Herve-Vandamme refractive index (n(HV)), the high (epsilon(infinity)) and the static (epsilon(o)) dielectric constants showed a decreasing trend with increasing reaction temperature. Weak ferromagnetic behavior was observed for the pure NiO samples, while the codoped samples with x > 4% showed linear M-H curves. The coercivety (H-c) decreased with reaction temperature, implying single-domain magnetization and sizes below the critical one. The magnetocrystalline anisotropy (K) indicated the softness of the prepared samples.