A.V. Rudenko, A.P. Apisarov, A.V. Isakov, O.V. Grishenkova, Yu.P. Zaykov.
ABSTRACT
The (CsCl–NaCl–KCl)eut – IrCl3 melt is promising for the production of iridium coatings and composite materials. The liquidus temperature and electrical conductivity were determined for several compositions of this melt by thermal analysis and impedance spectroscopy. The temperature ranges of liquidus (753–983) ± 5 К and solidus (751–755) ± 4 К are established and the corresponding part of the phase diagram for the quasi-binary system (CsCl–NaCl–KCl)eut – (0–2.12 mol. %) IrCl3 is plotted. It is shown that the lowest liquidus temperature is observed for the melt containing 1.4 mol. % IrCl3. An increase in the liquidus temperature in molten mixtures with the concentration of more than 1.5 mol. % IrCl3 is explained by the formation of the Cs3IrCl6 compound, which was detected by XRD analysis. It was found that the specific electrical conductivity of the tested melts (in the homogeneity region) linearly decreases with decreasing temperature and increasing IrCl3 concentration. The coefficients describing the temperature dependences of the electrical conductivity of (CsCl–NaCl–KCl)eut – (0–2.12 mol. %) IrCl3 melts were determined. For all studied iridium-containing compositions, the average value of the temperature coefficient was (2.35 ± 0.02) ∙ 10–3 Ω–1cm−1K−1. The addition of 1 mol. % IrCl3 leads to a decrease in electrical conductivity by about 7%. It was found that the operating temperature can be reduced to ~800 K in the melt with iridium trichloride concentrations of 1.4–1.5 mol. %; the process temperature can vary from 850 to 1030 K at a lower and higher IrCl3 content depending on the electrodeposition conditions.
KEY WORDS:
iridium, chloride melt, quasi-binary phase diagram, electrical conductivity
DOI: 10.31857/S0235010620060109