The structure,the morphology and the thermal,optical and the surface properties of nanocrystalline CeO2 doped with Mn have been studied by X-ray diffraction (XRD),field-emission transmission electron microscopy (FE-TEM),energy-dispersive X-ray analysis,thermogravimetric analysis,UV-Vis absorption spectroscopy and Fourier transform infrared spectroscopy.The XRD results confirmed the successful incorporation of Mn into the CeO2 lattice through the formation of nanoscale face-centered cubic solid solution.The FE-TEM observations supported the nanocrystalline nature of the solid solutions.The presence of structural defects and their role on the band gap have been discussed on the basis of absorption spectral studies.The structural differences correlate with results from temperature-programmed reaction (TPR) experiments with H2 consumption.The TPR measurements showed an enhanced bulk reduction at much lower temperatures,indicating increased oxygen mobility in the samples,which enable to enhanced oxygen diffusion at lower temperatures.