Structural and microstructural evolution due to increasing Co substitution in Ni1−xCoxFe2O4: An X-ray diffraction study using the Rietveld method

• Published in: Materials chemistry and physics Vol. 128; no. 3; pp. 365 - 370
• Main Authors: Mukherjee, R, Sahu, T, Sen, S, Sahu, P
• Format: Journal Article
• Language: English
• Published: 15-08-2011
• Subjects: Diffraction; Doping; Evolution; Ferrites; Microstructure; Particle size distribution; Spinel; Unit cell
• ISSN: 0254-0584
• DOI: 10.1016/j.matchemphys.2011.02.060

The effect of increasing Co substitution on the structural and microstructural evolution in AB2O4 type spinel ferrites: Ni1-xCoxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) was studied by XRD using Rietveld analysis. The specimens were synthesised by the organic precursor method. Structural refinement revealed that the pure NiFe2O4 was not an exact inverse spinel and about 11% of Ni2+ ions occupied the tetrahedral (A) sites. Increasing Co concentrations had the effect of increasing the ratio of [Fe3+]B/[Fe3+]A and a gradual expansion of the ferrite unit cell. The microstructural refinement estimated that the particle size ranged from 31 to 61 nm, which gradually increase with increasing Co doping accompanied by almost negligible lattice micro strains (approximately 10 exp(-4)). The corresponding particle size distribution for each specimen was obtained from the XRD data from the basic assumption that the spherical nanoparticles followed the log-normal distribution. The size distribution for the pure NiFe2O4 was also estimated from TEM and agreed well with that obtained by the diffraction data analysis.