Process for the production of superconducting monocrystals of iron chalcogenides of general formula FeTe0.5Se0.5

摘要

The invention relates to the technology of superconducting materials, in particular, to the production of monocrystals by the method of crystallization from melts.The process for the production of superconducting monocrystals of iron chalcogenides of general formula FeTe0.5Se0.5 consists in that preliminarily the initial materials selenium and tellurium are purified by zone melting, and iron pellets are subjected to mechanical cleaning, and then is performed the loading of initial materials into an evacuated vial, melting of the mixture by heating, exposure of the molten mixture at a temperature exceeding the component most refractory phase melting temperature with subsequent cooling and quenching. At the same time, heating of mixture is carried out at a rate of 2…5°C up to 600°C, is exposed for 20…24 hours, then is performed the stepwise heating with the step of 50°C at a rate of 1°C/min and exposure between steps for 8…10 hours up to reaching the temperature of 1100°C , at which the melt is exposed for 60…72 hours, then it is cooled at a rate of 2…60°C/hour up to a temperature of 420°C, at which the material is homogenized for 70…100 hours, and then it is carried out the quenching by placing the vial in a liquid at a temperature not exceeding 0°C. To obtain monocrystals of larger dimensions the obtained monocrystals are additionally milled in oxygen-free medium containing no water vapors, are heated into an evacuated vial at a rate of 5°C/min up to a temperature of 1100°C, at which the melt is exposed for 60…72 hours, then it is cooled at a rate of 2…60°C/hour up to a temperature of 420°C, at which the material is homogenized for 70…100 hours, and then is quenched by placing the vial in a liquid with a temperature not exceeding 0°C.