Glass-like dielectric relaxation in C 5NH 6ClO 4

Abstract

Detailed dielectric measurements have been carried out in polycrystalline pyridinium perchlorate C 5NH 6ClO 4 at temperatures of 100 K≤ T≤280 K and frequencies of 10 Hz ≤ ν ≤ 10 5 Hz . Besides the known dielectric anomalies at 248 and 233 K, a glass-like dielectric relaxation is clearly observed at temperatures below 233 K. The frequency dependence of the dielectric constant is interpreted to originate from two different relaxation processes. The relaxation time for the dominant relaxation process is well described by an Arrhenius equation with the activation energy E = 3073 K and τ 0 = 6.2 × 1 0 − 12 s . The other weak relaxation process is also analyzed using the same equation with E = 1160 K and τ 0 = 1.5 × 1 0 − 5 s . The dominant relaxation process is considered to arise from the coupled reorientation of the pyridinium cation and perchlorate anion, while the weak one seems to be attributed to the ferroelectric domain wall motion. This suggests that the phase below 233 K can be described as a mixed phase comprising the dipolar glass and ferroelectric states.