Crystallite Size and Compressive Lattice Strain in NiFe2O4 Nanoparticles as Calculated in Terms of Various Models: Influence of Annealing Temperature

Abstract

NiFe2O4 nanoparticles were synthesized by HMTA-assisted hydrothermal method, annealed at 600, 800, and 1000°C for 4 h, and characterized by XRD and high-resolution SEM. As the Debye–Scherer formula gives only rough estimation for crystallite size D and micro strain e, so we used Williamson–Hall (WH) plot and size–strain (SS) plot methods to study relative contribution from crystallite size and lattice strain to crystal structure of synthesized ferrites. The values of D and e were evaluated in terms of several models based on the Debye–Scherer formula (SM), modified Scherer formula (MSM), WH plot method (WHM), and SS plot method (SSM). It has been found that the size–strain method gives best fit and is most suitable for estimations of crystallite size. The WHM and SSM results are indicative of the occurrence of compressive strain in all studied crystals. Crystallite size was found to increase while micro strain, to decrease with increasing annealing temperature.