Electrolytic Coloration Of Oxygen-Doped Sodium Chloride Crystals And Mechanism Of Production And Transformation Of Color Centers

Oxygen-doped sodium chloride crystals were successfully colored electrolytically for the first time by using our homemade electrolysis apparatus, and a lot of color centers were produced in colored crystals. Spectral measurement and analysis were performed systematically to the colored crystals, and some spectra were decomposed reasonably. Production and transformation of color centers were explained. By using measured current-time curves, process and mechanism of production of color centers were further explained. The mechanisms, given by our research group, of the production and transformation of the color centers were further proved experimentally according to the present results of the verification experiments.By electrolysis using a pointed cathode, a lot of V2m, V, O2--Va+ complex, F, R1,R2 and M centers were produced in the colored oxygen-doped sodium chloride crystals. Because anion impurities prevent formation of secondary alkali cathode, oxygen-doped sodium chloride crystals are hardly colored electrolytically using the traditional electrolysis method. Success of this work should mainly benefit appropriate electrolysis temperatures and voltage as well as unique anode structure of used electrolysis apparatus, which makes V centers produced firstly inside crystals nearby anode. F centers are produced through photo-conversion of V color centers under illumination. Some F centers are aggregated into R1, R2 and M centers. Therefore, the original center produced by the electrolysis is V center. For further confirming this opinion, the previous sodium chloride, hydroxyl-doped sodium chloride, potassium-doped sodium chloride, potassium chloride, potassium bromide crystals and the present oxygen-doped sodium chloride crystal were colored electrolytically by using a graphite pointed cathode. It is shown that all these crystals were colored successfully because there were F absorption bands in all measured absorption spectra. During processes of electrolytic coloration of oxygen-doped sodium chloride crystals, current changes were observed, and current-time curves were plotted according to recorded current data. Formation mechanisms of current zones and their close relationship with production of color centers were explained.By electrolysis using a pointed anode, a lot of V and V2m centers were produced in the colored oxygen-doped sodium chloride crystals. Current-time curves were given, and formation mechanism of current zones is similar to that in case by electrolysis using a pointed cathode.