Glass-like dielectric relaxation in C5NH6ClO4

Detailed dielectric measurements have been carried out in polycrystalline pyridinium perchlorate C5NH6ClO4 at temperatures of 100 K≤T≤280 K and frequencies of 10Hz≤ν≤105Hz. 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=3073K and τ0=6.2×10−12s. The other weak relaxation process is also analyzed using the same equation with E=1160K and τ0=1.5×10−5s. 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.