Ionic conductivity of cold pressed nanoceramics Pr-=SUB=-0.9-=/SUB=-Pb-=SUB=-0.1-=/SUB=-F-=SUB=-2.9-=/SUB=- obtained by mechanosynthesis of components

Abstract

The impedance spectroscopy in the temperature range 302-779 K was used to study the ionic conductivity of the Pr0.9Pb0.1F2.9 nanoceramics, obtained by cold pressing of the powder, mechanically synthesized from components of PbF2 and PrF3. The studied material is the solid solution with tysonite-type structure (sp. gr. P3c1, Z=6) and lattice parameters a=7.0906(4) and c=7.2538(4) Angstrem. With increasing temperature, the conductivity of the ceramic increases from 1.9·10-5 to 6.7·10-2 S/cm, and the activation enthalpy of ion transport Delta Hsigma=0.407±0.005 and 0.345±0.005 eV at 302-502 and 502-779 K, respectively. The electrical conductivity mechanism is due to the migration of fluorine vacancies along the boundaries of nanocrystalline grains. The intragranular conductivity of ceramics is close to the electrical conductivity of a single crystal of the same composition. Cold pressed ceramics Pr0.9Pb0.1F2.9 can be used as a promising solid electrolyte in "room" fluorine-ion current sources. Keywords: ionic conductivity, impedance spectroscopy, fluorides, tysonite structure, cold pressed nanoceramics, mechanosynthesis.