Dielectric behavior and low temperature phase transition in NH4IO3

Abstract

The electrical properties namely ac conductivity σ(ω, T) and the complex dielectric permittivity (ε*) are measured at selected frequencies (5–100 kHz) as function of temperature (95 K < T < 280 K) for polycrystalline samples of NH4IO3. 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 σ(ω, T) obeys the power law. The trend of the temperature dependence of the angular frequency exponent s (0 < s < 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 NH4IO3; (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 X-ray 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.