Ionic Conductivity of Ce3NF6

Abstract

AbstractThe electrical conductivity of pressed polycrystalline Ce3NF6 pellets was measured using two‐probe measurements with two types of blocking contacts, namely platinum and LaF3, in the temperature range 300–450 K. The cerium nitride fluoride Ce3NF6 was prepared by the direct reaction of CeN and CeF3 at 1170 K. The DC measurements with the two types of blocking contacts proved that the conductivity of Ce3NF6 is mainly ionic due to fluoride ion transport, although the fluoride ion conductivity is much lower than known for the binary CeF3 phase. The analysis of the AC impedance measurements with both types of blocking contacts support the assumption of predominating fluoride ion transport. There was no indication for mobile nitride ions. Two relaxation processes were identified in the impedance spectra giving two maxima of the phase angle. The first one occurred at high frequencies around 200 kHz and was attributed to the bulk conductivity and dielectric response of Ce3NF6. The second relaxation process showed the maximum of the phase angle at medium frequencies in the range 100 Hz to 10 kHz. It was attributed to the impedance of high resistivity contacts between the grains. The transference number of electrons was lower than 0.1. The fluoride ion conductivity at 450 K was 5 × 10–7 S·cm–1 in the bulk and 7 × 10–9 S·cm–1 in the grain boundaries. The corresponding activation energy from the temperature dependence of the conductivity was 0.6 eV with no discernible difference of bulk and grain boundary contribution.