Synthesis and evaluation of Pb1−xSnxF2 by mechanical milling

Pb1−xSnxF2(x = 0.2–0.6) solid solutions were synthesized by mechanical milling (MM) from a mixture powder of α-PbF2 and SnF2. It was clarified that the solid solutions were synthesized not by heat but by the kinetic energy of the milling balls. For x = 0.2–0.6 except for x = 0.5, the mixtures changed to Pb1−xSnxF2, which has the iso-structure of β-PbF2. Furthermore, for x = 0.5, the mixture changed to PbSnF4. The crystallinity of the synthesized solid solutions using MM was improved by annealing at 200–500 °C, which is much lower than the maximum temperature at which the solid solution of Pb1−xSnxF2 (x < 0.23) was synthesized using a melting method. The Pb0.8Sn0.2F2 solid solution synthesized by MM showed a fluoride ion conductivity equal to that of the solid solution synthesized using a melting method. The fluoride ion conductivity of the pressed powder sample of the solid solution synthesized using MM increased with x from 0.2 to 0.5, showed a maximum of 1.6 × 10− 3 S/cm at x = 0.5 at room temperature, and decreased with increasing x of more than 0.5. After annealing the pressed powder, the fluoride ion conductivities of solid solutions for x = 0.5 showed the high values of 3 × 10− 2 S/cm at room temperature and 0.34 S/cm at 150 °C.