Because of its special electronic structure, high-purity germanium has been widely used in electronic devices, memory alloys, and atomic energy. 1121. The purity of germanium prepared by the calcium-thermal reduction method is low, and it generally cannot meet the requirements of hi-tech products. For further purification of low-purity germanium. The vacuum distillation method for purifying DyHo, Er has been reported in many reports|3~61; however, due to the high melting point of yttrium and the low saturated vapor pressure near the melting point|71, there are few reports on the purification of yttrium by vacuum distillation. According to the physical properties of the crucible, in order to increase the distillation rate of the crucible, distillation is generally performed at a high temperature of 1900*C, so that impurities such as YF3, CaF3, Fe, Al, Cu, etc., which have similar vapor pressures to the crucible, remain in the substrate crucible. Into the distillation of metal, it seriously affects the purification effect of antimony, so the content of these impurities must be strictly controlled or effectively removed before distillation.
In this paper, YF3 was prepared by dry fluorination method, which can effectively control the oxygen content in the crucible prepared by the thermal reduction method. 8.1 Experiment 1.1 The purity of raw materials and equipment is more than 99.9%; the gas HF is pure 99.99%; 10kg high vacuum Induction Furnace; High Vacuum Distillation Tube Furnace; High Vacuum Arc Furnace; Infrared Thermometer.
1.2 Processes Calcium thermal reduction method to prepare yttrium: Y2O3 is fluorinated to YF3 using the provided method. The yttrium is prepared by a calcium-thermal reduction method in a vacuum induction furnace with a vacuum degree of 1×10 2 Pa, and refined at 1600° 0. After grinding, one sample was obtained for the electric arc furnace to smelt and purify.
Arc smelting and purifying: The arc smelting furnace has a vacuum degree of 1×10 4 Pa. Under argon protection, 1 sample is arc smelted, and the melting temperature is approximately 2200. The metal is completely melted and then polished for 2 min. This was repeated 4 times to obtain a 2 Torr sample prepared by arc smelting for further distillation purification.
Vacuum distillation purification: Using helium as a smelting vessel, a 1 mm thick blister sheet as a condensing hood and a cooling fin around the condensing hood, and a heat shield between the condensing hood and the helium to prevent condensation in the condensing hood during distillation. The metal is reflowed due to high temperatures.
The vacuum degree of the furnace body is 1×10 4 Pa, and the distillation temperature is constant at 1900° C. After cooling, 3 samples of high-purity metal helium are peeled off from the condensing hood.
1.3 Sample Testing The 1,2,3 samples were sent to Baotou Rare Earth Research Institute for analysis.
2 Results and Discussion 2.1 Experimental Results Table 1 shows the analysis results of the Baotou Rare Earth Research Institute analysis room. One of the samples is a crucible prepared by a calorimetric reduction method, 2 is a crucible purified by arc melting, and the third sample is purified by vacuum distillation. High * Communication Contact (E-mail: 15 Liu Wensheng a (Male 丨 Inner Mongolia a person E Master (lecturer research direction igil soil material. All Table 1 metal lanthanum non-rare earth impurity analysis results (X element 2.2 discussion 2.2.1 Calcium fever The crude ruthenium 1 sample prepared by the reduction method is a ruthenium prepared by the calorimetric reduction method. The analysis result of the sample 1 in Table 1 shows that the total rare earth content is only 99.51% and the content of the non-rare earth impurity is 4873X10, wherein CaNi, W, O, F, The content of N is very high, and it is known from the calcium-thermal reduction process that these impurities are introduced during the preparation process. When the YF3 is produced by the dry fluorination method, the material trough is made of pure Ni, and the vacuum heat-reducing method is used to prepare the niobium. Tungsten yttrium is used, Ca is a reducing agent, and F is present in yttrium in the form of YF3, CaF2YOF, etc. The main source of 0,N in yttrium is the Y0F compound remaining in the metal and the residual gas in the furnace to the reducing agent Ca and the liquid helium. Surface oxidation and nitridation Started.
2.2.2 Removal effect of impurities by arc smelting 2 The sample is prepared by smelting and purifying 1 sample by arc melting. The analysis results of 2 samples in Table 1 indicate that the total amount of rare earths is increased to 99.64%, and the content of non-rare earth impurities is reduced to 3671X1 (T6). Compared with 1 sample, the reduction of 10 - \ vacuum arc smelting method is very effective for removing impurities CaMg, F, S in thorium. The efficiency of the removal is: Ca, Mg is in the form of CaF2, MgF2, Ca, Mg, In the presence of simple substance, because its vapor pressure is much higher than that of the base metal, it easily evaporates in multiple high-temperature and high-vacuum arc melting processes, and when it exists in the form of compound, its density is lower than that of the base metal, and it is easy to be in the arc melting process. Miscellaneous, it can be effectively separated and removed after being polished by multiple melting and cooling.
Among them, YF3, CaF2 vapor pressure and Y vapor pressure are different, but the difference is not large, it is easy to cause pollution to the distillation metal, must be effective before distillation. According to YF3, CaF2 has a lower melting point and a lower density, and it can be effectively separated and removed by high-temperature arc melting method through multiple melting and cooling. Y0F has a high melting point and a very low vapor pressure. This type of fluorine arc smelting method is difficult to remove, so the arc still has 90% of the F content in the arc melting refining X104. The existence of impurity S is basically the same as that of F, such as yttrium sulfide. The compound-type impurity C exists in the form of niobium carbide. Niobium carbide is a high-melting rare earth compound with a density close to that of the matrix metal. It is not easy to be miscellaneous in the arc melting process, and the separation effect from the matrix metal is poor. The efficiency at the place is only 33.3%. 0, N, etc. did not go to the effect, where 0 content slightly increased. This is because the vapor pressures of FeAl, Ni, W, and CuMn are close to that of the matrix Y, and the melting process is not easy to evaporate and impurities cannot be created. The slight increase in the content of O in the arc melting process is due to the oxidation of the surface of the liquid helium by oxygen molecules in the residual gas in the furnace. 2.2.3 Effect of Vacuum Distillation on Removal of Impurities 3 Samples are prepared from vacuum distillation of 2 samples. The results of the analysis of 3 samples in Table 1 indicate that the total amount of rare earths is increased to 99.96%, and the content of non-rare earth impurities is reduced to 371X16. 2 Compared with the sample, the 3300X10-\ vacuum distillation method is very effective for removing the impurities O, N, C, W, MnNi in the crucible. The efficiency of the removal is: 9%. The impurities Al, Si, and CuF also have a certain removal efficiency. The melting points of W, Mn, and Ni are much higher than that of lanthanum. Non-rare-earth impurities O, N, C, and F exist in the form of high-melting compounds in the lanthanum, and their vapor pressures are much lower than those of the base metal. Under high temperature vacuum, these substances are difficult to evaporate and remain in the lower part of the crucible. The vapor pressures of the impurities Al, Si, and Cu are almost the same as those of the base metal, and the separation and removal effect is poor.
The main source of 89X10-\Oxygen content is caused by the oxidation of the helium vapor molecules by the oxygen in the residual gas in the furnace. If the vacuum of distillation equipment is continuously increased, the oxygen content in the helium will decrease. The melting point and vapor pressure of FeCu are very close to those of Y. Arc melting and distillation cannot be removed, and they are strictly controlled during the preparation process.
2.2.4 Effect of Tantalum Material and Mould on the Purity of Tantalum In the process of the preparation of Yttrium by calcium heat reduction, the Yttrium material may be tungsten or beryllium. This method exists in the production method of the present invention. A, mainly because of the reduction process / Y3C high temperature corrosion greater than tungsten crucible. Casting mold with cold water copper mold rather than cast iron mold, because the impurity FeCu in the arc melting and vacuum distillation can not be effectively removed, the cold water copper mold metal pollution is much smaller than the cast iron mold, and in the entire process is strictly prohibited FeCu pollution.
In the vacuum distillation purification process, germanium is selected, and powder sintered tungsten and molybdenum/niobium materials cannot be selected. The main reason is that tungsten, molybdenum powder, and fluxes when sintering tungsten and molybdenum do not volatilize and condense metal in the hood under high temperature and high vacuum conditions. Condensers should be selected thorium tablets, molybdenum tablets can not be used, thorium dissolved corrosion at high temperatures is very serious, molybdenum will cause metal pollution.
3 Conclusion The vacuum arc melting method is very effective for removing the impurities CaMg, F, S in the crucible; the vacuum distillation method is very effective for removing the impurities 0, NC, W, MnNi in the crucible, and also has certain removal of the impurities Al, Si, Cu, F. effect. The two purification methods are very complementary, and the combined use of the non-rare earth impurities in the yttrium can be reduced from 4873X10 to 371X10-, and the purity from 99.51% to 99.96% is an effective method for the preparation of high purity yttrium. This method is also suitable for the purification of other rare earth metals.
Non-rare earth impurities in high-purity germanium are sourced from raw materials and preparation processes. In order to reduce the content of various impurities in the product, tungsten crucibles and cold water copper molds are used in the calcium heat reduction process, and crucibles are used in the vacuum distillation process. The device uses cymbals. The influence of the crucible material and the mold used in the purification of the metal crucible on the purity of the metal crucible was discussed.
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