A series of Ni1-xCuxFe2O4 (0 <= x <= 0.5) spinels were synthesized employing sol-gel combustion method at 400 degrees C. The decomposition process was monitored by thermal analysis, and the synthesized nanocrystallites were characterized by X-ray diffraction, transmission electron microscopy, infra-red and X-ray photoelectron spectroscopy. The decomposition process and ferritization occur simultaneously over the temperature range from 280 degrees C to 350 degrees C. TEM indicates the increase of lattice parameter and particle size with the increase of copper content in accordance with the XRD analysis. Cu2+ call enter the cubic spinel phase and occupy preferentially the B-sites within x = 0.3, and redundant copper forms CuO phase separately. A broadening of the O 1s region increases with the increment of copper content compared to pure NiFe2O4, showing different Surface oxygen species from the spinel and CuO. Cu2+ substitution favors the occupancy of A-sites by Fe3+. (C) 2009 Elsevier Ltd. All rights reserved.