The Intrinsic Fluorine-Ion Conductivity of Crystalline Matrices of Fluoride Superionics: BaF2 (Fluorite Type) and LaF3 (Tysonite Type)
- 3 Downloads
The intrinsic fluorine-ion conductivity σlat of BaF2 (CaF2 fluorite type) and LaF3 (tysonite type) crystals is studied by the impedance spectroscopy method. These compounds represent two major structural types taken as the basis to form the best nonstoichiometric fluorine-conducting solid electrolytes. The conductivity σlat caused by thermally activated defects is manifested in the field of high temperatures, where conductometric measurements are complicated by pyrohydrolysis. The experiments carried out in inert atmosphere with application of the impedance method have for the first time produced the reliable values of σlat of fluoride crystals in conditions of suppression of pyrohydrolysis (BaF2) or partial pyrohydrolysis (LaF3). Values of the σlat at 773 K for BaF2 and LaF3 crystals grown from melt by the Bridgman method using the vacuum technology are 2.2 × 10–5 and 8.5 × 10–3 S/cm differing by a factor of ~400. The tysonite structural type has been proved feasible for making high-conductivity solid fluoride electrolytes based on the analysis of energy characteristics of formation and migration of anionic defects.
This study was supported by the Ministry of Science and Highter Education of the Russian Federation within the State assignment of the Federal Scientific and Research Center of Crystallography and Photonics, Russian Academy of Sciences.
The authors are grateful to O.V. Glumov (St. Petersburg State University, St. Petersburg) for LaF3 crystal provided for experiment.
- 3.B. P. Sobolev, N. I. Sorokin, and N. B. Bolotina, in Photonic and Electronic Properties of Fluoride Materials, Ed. by A. Tressaud and K. Poeppelmeier (Elsevier, Amsterdam, 2016), p. 465.Google Scholar
- 7.B. P. Sobolev, The Rare Earth Trifluorides, Pt. 1: The High Temperature Chemistry of Rare Earth Trifluorides (Inst. Kristallogr., Inst. d’Estudis Catalans, Moscow, Barcelona, Spain, 2000).Google Scholar
- 9.A. A. Potanin, Zh. Ross. Khim. Ob-va im. D. I. Mendeleeva 45, 58 (2001).Google Scholar
- 12.A. Hammou, M. Duclot, and V. A. Levitskii, J. Phys. (Fr.) 37, 7 (1976).Google Scholar
- 17.I. V. Murin, O. V. Glumov, and Yu. V. Amelin, Zh. Prikl. Khim. 53, 1474 (1980).Google Scholar
- 18.A. Roos, A. F. Aalders, J. Schoonman, A. F. M. Arts, and H. W. de Wijn, Solid State Ionics 9–10, 571 (1983).Google Scholar
- 19.A. V. Chadwick, D. S. Hope, G. Jaroszkiewicz, and J. H. Strange, in Fast Ion Transport in Solids, Ed. by P. Vashishta, N. Mundy, and G. K. Shenoy (Elsevier, North Holland, Amsterdam, 1979), p. 683.Google Scholar
- 21.N. I. Sorokin and B. P. Sobolev, in Proceedings of the 1st Russian Crystallographical Congress, Moscow, 2016, p. 413.Google Scholar
- 22.I. V. Stepanov and P. P. Feofilov, The Growth of Crystals (Akad. Nauk SSSR, Moscow, 1957), p. 229 [in Russian].Google Scholar
- 23.V. A. Sokolov, Tr. GOI 54, 21 (1983).Google Scholar
- 24.G. G. Glavin and Yu. A. Karpov, Zavod. Lab. 30, 306 (1964).Google Scholar
- 28.H. D. Wiemhofer, S. Harke, and U. Vohrer, Solid State Ionics 40–41, 433 (1990).Google Scholar
- 33.R. I. Efremova and E. V. Matizen, Izv. SO AN SSSR, Ser. Khim. 2, 3 (1970).Google Scholar
- 34.W. Shroter and J. Nolting, J. Phys. (Fr.) 41, 6 (1980).Google Scholar
- 36.A. B. Lidiard, Crystals with the Fluorite Structure, Ed. by W. Hayes (Clarendon, Oxford, 1974), p. 101.Google Scholar
- 37.S. Kh. Ait’yan and A. K. Ivanov-Shits, Sov. Phys. Solid State 32, 795 (1990).Google Scholar
- 38.S. M. Shapiro, Superionic Conductors, Ed. by G. D. Ma-han and W. L. Roth (Plenum, New York, 1976), p. 261.Google Scholar
- 40.W. Bollmann, Cryst. Res. Technol. 16, 1039 (1981).Google Scholar
- 41.P. W. M. Jacobs and S. H. Ong, Cryst. Lattice Defects 8, 177 (1980).Google Scholar