The diffraction contrast in the X-ray topographs, taken for the crystal face parallel to the c-axis of the α-LiIO3 single crystals, appears to change remarkably under the action of an applied DC field along the c axis. The contrast in the topographs is restored after the removal of the applied field. After either turning on or turning off the DC voltage, relaxation processes are observed in both the change and the restoration of the diffraction contrast in the X-ray topographs. The change of the contrast depends on the polarity and magnitude of the applied voltage, but appears to be independent of the wave length of the X-ray.The X-ray topographs taken under the condition that a DC field is applied to the crystal displays the macroscopic crystal defects decorated by the space charges. In other words, we can observe the originally undetectable defects, while the space charges accumulate on the crystal defects, the local lattice distortion around the defects is enhanced.