JPH0379413B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing high-purity tellurium, which is supplied as a raw material for semiconductor materials. [Prior Art] Conventionally, methods for producing high-purity tellurium include vacuum distillation of ordinary-grade metallic tellurium, zone refining, and refining tellurite acid and subjecting it to sulfite reduction. It's here. Separation of selenium is particularly difficult in vacuum distillation and zone refining methods, which are one of the purification methods for high-purity tellurium metal, and impurities such as sodium, calcium, and iron remain. However, it is difficult to achieve a purity of 99.9999% by weight or higher, and expensive equipment is required, leading to high costs. Furthermore, even in the method of purifying tellurite acid and subjecting it to sulfite reduction, the process is complicated, and problems such as selenium residue and sulfur pollution due to sulfurous acid make it difficult to achieve a purification effect that exceeds 99.9999% by weight. Obtaining tellurium was extremely difficult. [Problems to be Solved by the Invention] An object of the present invention is to provide a manufacturing method for obtaining highly purified tellurium more easily than before. [Means for Solving the Problems] The present invention provides tellurium tetrachloride by passing dry chlorine gas through ordinary grade metal tellurium, and distilling and refining the tellurium tetrachloride in a distiller to reduce the throughput by 5 to 15 times.
After separating and removing the initial distillation of tellurium tetrachloride corresponding to % by weight, the distillation process is carried out again and the obtained fraction is used as the main fraction to recover purified tellurium tetrachloride, and the purified tellurium tetrachloride is hydrolyzed with pure water. The method involves reducing the tellurium dioxide in a hydrogen stream. [Function] In the present invention, when distilling and refining tellurium tetrachloride, the initial distillate, which accounts for 5 to 15% by weight of the processed amount, is separated and removed because the proportion of the initial distillate to be removed is less than 5% by weight. Selenium, phosphorus, sulfur as low-boiling impurities,
This is because arsenic, antimony, tin, gallium, etc. remain in the main distillation, and as a result, the purity of high-purity tellurium is lowered, contrary to the purpose, and the proportion of the initial distillation to be removed exceeds 15% by weight. This is because not only the yield of available products decreases, but also the improvement in product purity becomes less significant. Furthermore, when reducing tellurium dioxide in a hydrogen stream, if the reaction temperature is less than 450°C, the reaction rate will be slow, resulting in extremely poor productivity and the reaction temperature will increase.
If the temperature exceeds 730°C, the reaction rate will be faster, but the tellurium dioxide will melt and react with the graphite boat, resulting in severe damage to the graphite board containing tellurium dioxide. Therefore, hydrogen reduction is preferably carried out at 450-730°C. By pre-grading the graphite board into which tellurium dioxide is charged and performing reduction, the reduced metal tellurium can flow along the slope, making it easy to separate the metal tellurium from unreacted tellurium dioxide. At the same time, it becomes possible to suppress the evaporation loss of metallic tellurium by keeping the aggregate of metallic tellurium that has been separated from unreacted tellurium dioxide and accumulated at the bottom at a low temperature where it is difficult to evaporate. [Example] Example 1 560 g of metallic tellurium with a purity of 99.9% by weight was placed in a boat made of heat-resistant tempered glass, and the boat was further reduced in diameter.
A heat-resistant tempered glass tube with a length of 90 mm and a length of 2 m is inserted into the core tube of a tube furnace. Next, after replacing the inside of the furnace core tube with nitrogen glass, chlorine gas was replaced with 2
By heating the metal tellurium charge to 410°C for 3 hours while introducing it into the reactor core tube at a flow rate of /min, approximately 900 g of tellurium tetrachloride was produced while leaving approximately 80 g of unreacted material in the board. was able to be collected. After charging the tellurium tetrachloride obtained in this way into a flask made of heat-resistant tempered glass as a distillation device, the entire distillation system was replaced with nitrogen gas, the tellurium tetrachloride in the flask was heated to 430°C, and the flask was The reaction proceeded while keeping the condenser connected to the tube at 270°C. The reaction was stopped when the amount of tellurium tetrachloride accumulated in the receiver reached 96 g, and at this time, the tellurium tetrachloride accumulated in the receiver was separated out of the system as the first distillate, and then the first distillate was produced. The reaction was carried out again under the same conditions, and then 710 g of purified tellurium tetrachloride that had accumulated in the receiver was distilled off as the main distillate. 700% of the purified tellurium tetrachloride distilled as this main fraction
After dissolving in cc of pure water, use a stirrer to dissolve approx.
Hydrolysis was caused by dropping into pure water in a 10-capacity beaker stirred at a speed of 200 rpm to obtain tellurium dioxide as a white precipitate. This tellurium dioxide was subjected to repulp washing three times, then dehydrated and dried to obtain 380 g of high purity tellurium dioxide. Furthermore, 350 g of high-purity tellurium dioxide obtained in this way was placed in a graphite boat.
After charging a transparent quartz tube with a diameter of 90 mm and a length of 2 m into a tube furnace with a core tube, the reduction reaction was continued at 500°C while flowing hydrogen gas at a rate of 2/min into the core tube for 6 hours. After the reaction was completed, 205 g of tellurium metal was recovered. The metallic tellurium thus obtained was confirmed to have a purity exceeding 99,99999% as a result of mass spectrometry. Example 2 990 g of metallic tellurium with a purity of 99.9% by weight was placed in a 1-capacity heat-resistant tempered glass flask with three necks.
A capillary was placed in the side port, a mantle heater was heated, and when the metal tellurium reached 250°C, chlorine gas was blown in at a rate of 1.3 ml/min. In this case, the metallic tellurium first became black tellurium dichloride and became liquid. As chlorination continued, tellurium dichloride turned into tellurium tetrachloride, a orange-colored liquid. In this case, tellurium tetrachloride still contains a small amount of tellurium dichloride, so the mantle heater should be
It was heated to ℃ and distilled into another flask with a chlorine stream to completely convert it into tellurium tetrachloride. The tellurium tetrachloride thus obtained was transferred to a distiller, the inside of the distiller was purged with nitrogen, and then a mantle heater was heated to 420°C. After distillation of tellurium tetrachloride started and when 146 g was distilled, the distillate inlet pipe was switched, the first distillate and the main fraction were separated, and the subsequent distillate was used as the main distillate.
1590g was recovered. After dissolving 500 g of tellurium tetrachloride from this distillation in 500 c.c. of pure water, it was gradually dropped into pure water 8 placed in a 10-volume flask while stirring with a stirrer for hydrolysis. This white precipitate, tellurium dioxide, is separated from the supernatant by decantation.
After adding new pure water 3 and repeating repulp washing 5 times, and performing repulp washing with hot pure water 3 times, high purity tellurium dioxide 248 was obtained by filtration and drying.
I got g. 200 g of this high-purity tellurium dioxide was placed in a quartz board, and the inner diameter of 90 mm and length of 2 m was charged into a core tube made of transparent quartz tube.
Tellurium dioxide was reduced to metallic tellurium by maintaining the tube furnace at 700° C. while introducing the gas at a rate of 1/min.
The metallic tellurium inside the board eventually evaporated and was recovered in the form of tellurium melt and tellurium powder in the air-cooled section inside the board. The tellurium melt and tellurium powder thus obtained were heated to 500° C. in a hydrogen stream to obtain 149 g of metallic tellurium. The purity of the metal tellurium obtained by mass spectrometry was confirmed to be over 99.99999% by weight. Table 1 shows the mass spectrometry values of the examples of the present invention in comparison with high purity metallic tellurium obtained by the conventional method.

〔Effect of the invention〕

As is clear from the mass spectrometry results, the method of the present invention has a remarkable purification effect especially on low-melting point impurities, making it possible to extremely easily obtain high-purity tellurium with a purity of 99.99999% by weight or more.

Claims (1)

[Claims] 1 When ordinary grade metal tellurium is passed through dry chlorine gas to form tellurium tetrachloride, and the tellurium tetrachloride is purified by distillation using a distiller, 5 to 15% by weight of the amount to be processed is used.
After separating and removing the initial distillation of tellurium tetrachloride, the distillation process is carried out again and the obtained fraction is used as the main fraction to recover purified tellurium tetrachloride, and the purified tellurium tetrachloride is hydrolyzed with pure water. A method for producing high-purity tellurium, which comprises using tellurium dioxide as tellurium dioxide, and reducing the tellurium dioxide in a hydrogen stream.