The effect of Cd saturated annealing at 600^oC on electrical and optical properties of undoped CdTe was investigated by Hall effect, conductivity and photoluminescence measurements in the temperature interval of 4.2-300K. We observed that p-to-n conversion occurs in p-CdTe during annealing, where converted n-type layer surrounds the p-type center of the sample (core). The thickness of the converted n-type layer detected by Electron beam induced current method (EBIC) was found close to the forth root of the annealing time and differs from standard diffusion behavior characterized by a square root dependence. High electron mobility 1200 cm²/Vs and carrier density 2x10¹⁴ cm^-3 at room temperature were observed in the n-type layer, which indicates high quality of the sample. Highly compensated donor level with ionization energy E_D~10meV was determined there. Anomalous conversion of the sample back to the p-type was observed after the long time annealing, when the core was annihilated. Electrical properties of as-grown p-type crystal and p-type core were not significantly changed by the annealing contrary to reconverted p-type, where the hole concentration decreased by several orders of magnitude. Purification of the n-type layer due to gettering of fast diffusing impurities into the core region during annealing was observed by photoluminescence, where the intensity of PL lines of the excitons bound to neutral acceptors (A^o,X) in the n-type layer is significantly reduced comparing with that of in as grown crystals.
Observed results are explained by a diffusion of Cd interstitials into the sample together with gettering of foreign rapidly diffusing acceptors in the core region and redistribution of impurity defects to the whole sample and formation of acceptor like defects after core annihilation.

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