Fluoride ion conductivity of solid solutions KxPb0.86-xSn1.14F4-x

Abstract

The electrical conductivity of solid solutions with tetragonal syngony formed in 0.86(xKF–(1–x)PbF2)–1.14SnF2 systems has been studied by 19F- -NMR and impedance spectroscopy. It was found that the Pb0.86Sn1.14F4 phase is characterized by better values of fluoride-ion conductivity than the β-PbSnF4 compound. It was found that the substitution of Pb2+ by K+ up to х = 0.07 in the structure of Pb0.86Sn1.14F4 contributes to increase in electrical conductivity by an order of magnitude relative to the original Pb0.86Sn1.14F4. The sample of composition K0.03Pb0.83Sn1.14F3.97 has the highest electrical conductivity (σ600 = = 0.38 S cm-1, σ330 = 0.01 S cm-1). The fluoride anions in the synthesized samples of KxPb0.86-xSn1.14F4-x solid solutions occupy three structurally nonequivalent positions. It is shown that with increasing temperature, there is a redistribution of fluorine anions between positions in the anion lattice, which results in an increase in the concentration of highly mobile fluoride ions, which determine the electrical conductivity of the samples.

Keywords

• solid electrolytes
• lead and tin fluorides
• heterovalent substitution
• impedance spectroscopy
• 19f nmr spectroscopy