Dielectric behavior and low temperature phase transition in NH₄IO₃

Abstract

The electrical properties namely ac conductivity (!, T) and the complex dielectric permittivity ("*) are measured at selected frequencies (5-100 kHz) as function of temperature (95 K 5 T 5 280 K) for polycrystalline samples of NH 4 IO 3 . The ferroelectric hysteresis loops and the X-ray diffraction pattern are also measured. The analysis of the data indicates that the compound undergoes a structural phase transition at $103 K and the behavior of (!, T ) obeys the power law. The trend of the temperature dependence of the angular frequency exponent s (0 5 s 5 1) suggests that the quantum mechanical tunneling model is the most likely one that describes the conduction mechanism. The core results of the article are: (1) the low temperature ac electrical parameters are measured for NH 4 IO 3 ; (2) the data indicate that the compound undergoes a structural phase transition at 103 K; (3) the originality of this transition has been confirmed by Xray diffraction; (4) no evidence for the existence of a ferroelectric transition at 103 K as mentioned earlier; and (5) the quantum mechanical tunneling is proposed as the main mechanism of the electric conduction.