Piezoelectric and dielectric relaxation in nickel iodine boracite at low temperature

Abstract

With a view to elucidating the anomaly of various physical properties found near 120K, the complex dielectric constant has been measured versus temperature (4K → 300K) and frequency (10kHz → 1MHz) and is compared to previous piezoelectric studies. Substantial shifts in temperature of the ε″-peak and 1/Q_m piezo-peak with frequency indicate a Debve type relaxation mechanism due to defects and exclude new phase transitions as previously claimed in literature. A similar, but weaker anomaly occurs near 15K. Relaxation times and activation energies are given.