ИСТИНА

The studies of K2PtF6 vaporization by Knudsen cell mass spectrometry were performed earlier [1, 2]. It was found in [1], the saturated vapor contains small amount of K2PtF6 molecules (~1%) and volatile products of thermal decomposition, KF and F, are the main components. When K2PtF6 was evaporated from nickel and platinum effusion cells the inclination of linear dependence ln(I(K+)×T)–1/T was found to be 29013 kJ/mol and referred to “sublimation enthalpy of KF from K2PtF6” [1]. The contrary result on vapor composition was obtained in [2]. Direct measurement of ion currents I(F+), I(F2+) and I(HF+) in the range 600-1063 K showed, that the thermal decomposition of K2PtF6 proceeds with very weak release of atomic fluorine [2]. The determination of molecular precursors for K+ (with the assumption that 100% of ion current I(K2F+) formed by electron ionization of K2F2 molecules) showed, in the range 1043-1093 K saturated vapor should contain up to 40% of particles, containing K and Pt, but not being the K2PtF6 molecules, according to [1]. Taking into account, that mass spectrum contained relatively intense signals KPtFn+ (n=0-3), we have supposed, that these particles are the volatile complexes with formula KPtFn+1 (n=1-4). In the present work the experimental consisted of three parts: 1) the determination of K2PtF6 heat of vaporization by K2PtFn (n=4-6) ion currents measuring; 2) the study of ionic vapor composition; 3) the study of sublimate and residue in a cell after vaporization by XRD and SEM/EDS. The electron ionization mass spectra were recorded with electron energy 45-60 eV. It was found, the ratio of intensities K2PtF4+:K2PtF5+:K2PtF6+=100:80:32 does not depend on temperature in the range 963-1100 K. The inclination of linear dependence ln(I×T)–1/T for ions K2PtF5+ and K2PtF6+ was found as 28210 and 28610 kJ/mol, respectively. The signals K+, K2F+, K2PtF4+, K3PtF6+, PtF4–, KPt2F8–, were found in the thermal emission mass spectra. The signals K2PtF4+, K3PtF6+ and KPt2F8– unambiguously show the presence of KPtF4 and K2PtF6 molecules in the saturated vapor. The sublimate, sputtered at cell temperature 1063-1070 K, was hydroscopic and had brown color. Its analysis by SEM showed the surface consist of grown together acicular crystals, in some places blurred owing to moisture absorption. The atomic ratio K/Pt=3.35 was found by EDS analysis. It confirms the above assumption about large amount of platinum-containing complexes in the saturated vapor (the partial pressures of platinum fluorides are not great, according to electron ionization mass spectrum). X-ray diffraction pattern of sublimate contained several intense reflexes, which were not identified. The phases KF, KF2H2O, K2PtF6, PtF3, PtF4 were absent. The residue in a cell was consisted of the phases K2PtF6, KNiF3 and Pt. It confirms the results obtained in [1, 2]. As a result of the present work the saturated vapor composition and heat of K2PtF6 vaporization were determined. This work was supported by Russian Foundation for Basic Research (project №05-03-32916a). 1. M.V. Korobov, E.B. Badtiev, G.F. Voronin, A.A. Bondarenko, L.N. Sidorov VINITI 19.02.79, № 608-79. 2. M.S. Leskiv, S.V. Abramov, L.I. Oleynik, A.V. Kepman, V.F. Sukhoverhov, Z. Mazey, J.V. Rau, N.S. Chilingarov, L.N. Sidorov Inorg. mat., 2005, 41, 1327-1333.