Preparation Of Electrolytic Coloration Appatatus And Spectral Property Of Color Centers In Electrolytically Colored Crystals

Alkali halide crystals can be colored by different ways. In our recentwork, the coloration ways of electron bombardment, γ-ray irradiation,two-photon absorption and xenon ion implantation were systematicallyinvestigated, however, electrolytic coloration was not involved in yet. In thepresent work, an electrolytic coloration apparatus with ingenious structureand excellent performance was carefully manufactured based on the presentcondition and previous researches, by which KCl crystals were successfullycolored. According to the design, the apparatus mainly consisted of heater,temperature controller and coloration cabinet. The resistance tube furnacewith DTR-temperature controller was used as the heater in order to obtainedan adjustable temperature range of 100 – 1000 oC, small temperaturefluctuation at fixed temperature and easy applications of voltage andprotective gas. The coloration cabinet has a pipe structure, its end with gasinlet is fixed and outlet end is mobile for ease of putting on or off the crystal.The other parts of the coloration cabinet except for the electrodes are made offireproofing and insulative materials. The electrodes composed with a pointedcathode and a flat anode are used, the cathode is made of tungsten and theanode of stainless steel. This structure is very favorable to the fixation andcoloration of the crystal. After assembled and adjusted, the colorationapparatus operates very well; the coloration cabinet has good obturation andthe electrodes have good electric conduction under the protection of the argon.The temperature of the coloration cabinet is stable and appears a smallerfluctuation. The apparatus is completely satisfied for present experiment. The KCl crystals were electrolytically colored with the apparatus at923K, 20 V and 575K, 600 V, respectively, and a lot of K, F, M4, R, M andsome unknown color centers were effectively produced. Spectralmeasurements at different positions on the colored crystals weresystematically carried out, the measured spectra were seasonably decomposed,and spectral parameters of the color centers were accurately determined. Thespectral analyses show that the concentrations of the color centers producedat the different conditions is different, low F-center and high aggregate-centerconcentrations were produced under the high temperature and low voltage,and quite the opposite under the low temperature and high voltage. Moreover,the concentration of the color centers produced by the electrolysis exhibits agradient diffusion in the colored crystals, namely, the near the cathode, thehigh concentration, which is an effective method for some applications withthe color centers. The production, decomposition, aggregate and conversionof the color centers in the electrolytically colored crystals weresystematically analyzed and investigated, and the formation and conversionmechanism of the color centers was briefly presented. The present results show that the apparatus has unique characteristics,which can not only satisfied for the present experimental requirements also beeasily and quickly manufactured at home. The operation performance of theapparatus is very well, and the KCl crystals can be effectively colored withthe apparatus, which have not only developed the methods for preparingmaterials for optical storage and laser with the color centers also laid afoundation of the further research based on the obtained rich spectral dataobtained from the colored KCl crystals.