Optimization of the Compositions of Solid Electrolytes Pb1 – xRxF2 + x with Fluorite-Type Structure in Conductivity and Thermal Stability

• Published in: Crystallography reports 2020, Vol.65 (1), p.98-105
• Main Authors: Sorokin, N. I., Sobolev, B. P.
• Format: Article
• Language: English
• Subjects: Composition; Conductivity; Crystallography and Scattering Methods; Current sources; Electrical resistivity; Fluorine; Fluorite; Ion currents; Ions; Molten salt electrolytes; Optimization; Phase diagrams; Physical Properties of Crystals; Physics; Physics and Astronomy; Rare earth elements; Room temperature; Single crystals; Solid electrolytes; Thermal stability
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774520010241

The compositions of nonstoichiometric phases Pb 1 –   x R x F 2 +   x (CaF 2 type, R is a rare-earth element) have been optimized with respect to the ionic conductivity and thermal stability based on the temperature measurements of the electrical conductivity of single crystals and alloys, in dependence of their R 3+ ionic radius and R F 3 content, and on the analysis of the phase diagrams of the PbF 2 – R F 3 systems. It is shown that Pb 0.95 Yb 0.05 F 2.05 and Pb 0.9 Sc 0.1 F 2.1 crystals have the highest conductivities among the Pb 1 –   x R x F 2 +   x phases (σ 500 K = 9.3 × 10 –3 and 2.0 × 10 –2 S/cm and σ 293 K = 1.4 × 10 –6 and 1.5 × 10 –4 S/cm, respectively). The conductivity σ 293 K of the solid electrolyte Pb 0.9 Sc 0.1 F 2.1 is sufficient for using it in room-temperature fluorine-ion sensors and current sources.