Funct. Mater. 2025; 32 (3): 429-440.

doi:https://doi.org/10.15407/fm32.03.429

Synthesis and electrophysical properties of fluoride conducting phases Ba1-y-xLaxSn1+yF4+x

O.V. Lysenko1, R.M. Pshenychnyi2, A.O. Omelchuk1

1V.I. Vernadsky Institute of General and Inorganic Chemistry, NAS of Ukraine 32-34, Acad. Palladina Ave., 03680 Kyiv, Ukraine
2Sumy State University 116, Kharkivska st., 40007 Sumy, Ukraine

Abstract: 

In this paper, the electroconductive properties of solid non-stoichiometric phases formed in the BaF2–LaF3–SnF2. The Ba0.86-xLaxSn1.14F4+x and Ba0.8-xLaxSn1.2F4+x phases containing up to 0.12 mole fractions lanthanum were synthesized by the method of co-precipitation of BaF2 and LaF3 followed by sintering with SnF2. The crystal lattice of the synthesized compounds corresponds to the tetragonal syngony (space group P4/nmm) and is isostructural to BaSnF4. The electrical conductivity of the synthesized phases depends on the pressure at which the samples were prepared. Samples made at a pressure of 9.8 MPa have the highest conductivity. The electrical conductivity of the synthesized solutions of heterovalent substitution Ba0.86-xLaxSn1.14F4+x and Ba0.8-xLaxSn1.2F4+x is higher than the conductivity of the initial non-stoichiometric phases Ba0.86Sn1.14F4.00 and Ba0.80Sn1.20F4.00, and the activation energy of electrical conductivity is lower. An increase in the substituent amount: to 0.12 for Ba0.86-xLaxSn1.14F4+x and to 0.10 for Ba0.8-xLaxSn1.2F4+x positively affects the electrical conductivity of the obtained electrolytes. Analysis of the isothermal conductivity surface of the fluoride conducting phases Ba1-y-xLaxSn1+yF4+x x≤0.12, y≤0.2 indicates that the conductivity of solid electrolytes increases with increasing concentration of lanthanum and tin in the material. The electronic component of conductivity for the samples with different cationic composition, and the charge transfer numbers of fluorine anions were estimated. The conductivity of all synthesized phases is determined by fluorine anions, the charge transfer numbers are close to unity.

Keywords: 
fluoride-conducting phases, fluorides of tin, barium, lanthanum, solid substitution solutions, electrical conductivity, X-ray diffraction, voltammetry.

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