  Local and long range structure, optical and photoluminescence properties of
sol-gel synthesized Ce1-xNixO2 nanostructures have been studied. The crystal
structure, lattice strain and crystallite size have been analyzed. A decrease
in lattice parameter may be attributed to substitution of Ce with smaller Ni
ion. UV-Vis measurement is used for studying the effect of Ni substitution on
bandgap and disorder. The bandgap decreases with Ni substitution and disorder
increases. The PL spectra show five major peaks attributed to various defect
states. The PL emission decreases with Ni substitution owing to increase in
defects which acts as emission quenching centers. The lattice disorder and
defects have been studied using Raman spectroscopy. Raman measurement shows
that oxygen vacancies related defects are increasing with Ni substitution which
causes changes in optical and PL properties. Local structure measurements show
that Ni substitution leads to oxygen vacancies which does change host lattice
structure notably. Ce4+ to Ce3+ conversion increases with Ni substitution.
