XRD, microstructural and EPR susceptibility characterization of combustion synthesized nanoscale Mg1−xNixO solid solutions Original Research Article

The lattice parameter a(x) of the stoichiometric Mg1−xNixO (0⩽x⩽1) solid solutions prepared by urea-based combustion synthesis with fuel to oxidizer ratio (ψ=1) was determined by X-ray diffraction. It was found that the dependence of the lattice parameter a(x) on the composition deviated more from the linear Vegardʹs model (VM) when compared to Kuzmin–Mironova (KM) model. a(x) in the Mg1−xNixO system differs nontrivially from the predictions of both VM and KM models. For x=0.4 (Mg0.6Ni0.4O), the maximum deviation was about 2 and 1.7 pm, respectively. The increase in the intensity of (1 1 1) peak in XRD with increase of nickel concentration confirms that the substitution induces changes at the unit cell level. Nelson–Riley function (NRF) and Williamson–Hall plots are used to calculate micro strain in the solid solution. This analysis indicates that the micro strain is maximum for the compositions 60–40 (Mg0.6Ni0.4O), 50–50 (Mg0.5Ni0.5O) and 40–60 (Mg0.4Ni0.6O). The crystallite size was estimated using Williamson–Hall plot. We conclude that almost similar sized crystallite is formed in all the compositions studied. Porosity determined using XRD increases with a raise in the nickel concentration. The SEM morphology provides corroborative evidence. EPR susceptibilities of solid solution Mg1−xNixO are determined at room temperature. Variable temperature of EPR allowed to check the Curie–Weiss law for solid solution. The linearity of CM(x) and Θ(x) with concentration of nickel has ruled out chemical clustering in the samples.