高硒碲一次真空蒸馏脱硒、钠制备高纯碲工艺探究

Preparation of high purity tellurium with high selenium tellurium by one vacuum distillation process removing selenium and sodium

高纯碲是广泛应用于红外探测、核辐射探测、光伏、制冷等领域的关键半导体材料,其应用范围受碲纯度限制。目前制备6 N、7 N级高纯碲的主流工艺为“真空蒸馏-通氢区熔”,但对于高硒原料,该工艺流程所制备产品难以达标。本文以4 N级碲为原料(主要杂质元素为硒、钠,硒含量为6.2×10^(-6)),进行了高纯碲制备试验。通过分析在同一冷凝位置内、外层杂质含量差异,发现了碲冷凝过程中存在“冷凝区滑移”现象,造成低沸物杂质与产品混杂问题;试验还表明,延长原料恒温预热时间和加入高纯石英也有利于碲的提纯。针对上述问题,对原工艺进行改进,在延长原料恒温预热时间至70 min、预烘冷凝器、于原料碲中掺入高纯石英碎片的条件下,实现在通氢区熔工序前高效分离原料碲中的硒和钠,可将4 N级高硒冶炼碲锭经一次蒸馏制得6 N级高纯碲。该改进后工艺无需在真空蒸馏工艺中通氢,即可一次蒸馏制备6 N级高纯碲,大幅节约制造成本,且为采用4 N级高硒碲为原料制备7 N级超高纯碲提供了条件。

High purity tellurium is a key semiconductor material widely used in infrared detection,nuclear radiation detection,photovoltaic,refrigeration and other fields.Its application range is limited by the purity of tellurium.At present,the mainstream process for preparing 6N and 7N high-purity tellurium is vacuum distillation-hydrogen zone melting process,but for high-selenium raw materials,the products prepared by this process are difficult to meet the standards.In this paper,4N grade tellurium was used as raw material(the main impurity elements were selenium and sodium,and the selenium content was 6.2×10^(-6)),and the preparation experiment of high purity tellurium was carried out.By analyzing the difference of impurity content in the inner and outer layers at the same condensation position,it is found that there is a phenomenon of‘slip in the condensation zone’,which causes the problem of low boiling impurity and product mixing.The experiment also shows that prolonging the preheating time of raw materials and adding high purity quartz also affect the purification of tellurium.In view of the above problems,the original process is improved.Under the conditions of prolonging the constant temperature preheating time of raw materials to 70 min,pre-baking the condenser,and adding high-purity quartz fragments to the raw material,the selenium and sodium in tellurium can be efficiently separated before the hydrogen zone melting process.The improved process can prepare 6N grade high purity tellurium by one distillation without hydrogen in the vacuum distillation process,which greatly saves the manufacturing cost,and provides conditions for the preparation of 7N grade ultra-high purity tellurium with 4N grade high selenium tellurium.