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Nickel substitution at the cobalt site in Na0.75CoO2 induces an upturn in the resistivity on lowering the temperature, with the metal-to-insulator transition temperature (T MIT ) increasing with the Ni content. Low temperature far infrared measurements on polycrystalline samples of Na 0.75 CoO 2 and Na 0.75 Co 0.95 Ni 0.05 O 2 , the latter having T MIT ∼ 175 K, have been carried out. Dramatic changes in the Na mode frequencies, and relative intensities of the out-of-plane modes corresponding to the two Na sites are observed, coincident with the MIT in Na0.75Co0.95Ni0.05O2. It is argued that these changes are associated with a charge ordering of the CoO 2 layer, associated with the metal-insulator transition.