ТРАНСФОРМАЦӀЯ ПРИРОДИ ПРОВӀДНОСТӀ ВИСОКОПРОВӀДНИХ ХАЛЬКОГЕНӀДНИХ РОЗПЛАВӀВ В БӀК ЇХ ЕЛЕКТРОЛӀТИЧНОЇ ЗДАТНОСТӀ

Abstract

Ibe aim of this work is to study the nature of the conductivity of melts of iron chalcogenides (Fe-Se, Fe-Te, FeS-Na2S) and the conditions of its possible transformation in order to bring the high-conductivity melt to a state suitable for electrolytic decomposition into metal and chalcogen. To solve this problem, a set of methods was used - electrical conductivity (ж), thermo-EMF (a), polarization characteristics (І-V) and electrolysis (n). ж of high-conductivity melts was investigated by the four-probe method on a direct current in a quartz U-shaped cell of capillary type with graphite electrodes and molybdenum current leads in the direct current mode. The systematic error due to the accuracy class of the devices is 1%; random - does not exceed 1%. Low ж melts were studied by the two-probe AC method. Due to the high chemical aggressiveness of FeS-Na2S melts, a measuring cell with an alundum capillary was developed. Random error when measuring ж two-probe method on alternating current is 3%, systematic - is within 2%. Thermo-EMF was measured by the differential method with respect to tungsten probes. The temperature difference between the probes was recorded by a differential thermocouple. Systematic error in measuring thermo-EMF was 2%, random - 1.5%. Polarization characteristics were removed by the method of direct current in a simple cell without separation of electrode spaces. In cells of this type in an argon medium over the melt and experiments on electrolysis were performed. It is established that all samples are characterized by significant values of electrical conductivity (of the order of thousands of Sm/cm) and its negative temperature coefficients; the absolute thermo-EMF of all samples is units of цУ/deg. Melts are qualified as electron-ion (polyfunctional) conductors with a predominant metallic contribution to the conductivity. The introduction of Na2S into the FeS melt leads to a decrease in electrical conductivity and the transformation of its temperature dependence to the inherent ionic compounds. The melt electrolysis of the FeS-Na2S system with the production of iron was carried out. Thus the possibility of transformation of the nature of conductivity of highly conductive chalcogenide melts of iron towards their electrolytic ability is proved. The obtained results must be taken into account when using electrochemical technology of processing polymetallic sulfide ores, which include metal chalcogenides of iron family. KEYWORDS: MELTS, IRON CHALCOGENIDES, NATURE OF CONDUCTIVITY, ELECTRIC CONDUCTIVITY, TRANSFORMATION, ELECTROLYTIC CAPACITY.