Dipole glass behavior in ferroelectric pyridinium periodate Original Research Article

Detailed investigations have been performed on the dielectric behavior in polycrystalline pyridinium periodate C5NH6IO4 at temperatures View the MathML source100K≤T≤340K and frequencies View the MathML source10Hz≤ν≤105Hz. A remarkable dielectric relaxation is clearly observed at temperatures below 250 K. The frequency dependence of the dielectric constant is analysed by use of a sum of two kinds of relaxation process with different strength. The relaxation time for the dominant relaxation process obeys the Arrhenius law with the activation energy View the MathML sourceE=3869±15K and the pre-exponential factor View the MathML sourceτ0=3.3×10−12s. The dominant one is regarded as clear evidence of the dipole glass state in C5NH6IO4. Its origin is thought to be the coupled reorientation of the pyridinium cation and the IO4 anion. The overall temperature dependence of the relaxation time for the other weak relaxation process shows a quite different pattern which can hardly be described by the Arrhenius law. The weak one is considered to originate from the ferroelectric domain wall motion.