Electric properties of NH 4Sn 2F 5 polycrystals in the frequency range from 20 to 3.2 · 10 10 Hz

Abstract

The ionic conductivity ( σ ac) and the real part of complex dielectric permittivity (ε′) of F − conductor NH 4Sn 2F 5 have been investigated between 300 and 380 K in the frequency range from 20 to 3.2 · 10 10 Hz. The crystals NH 4Sn 2F 5 at the temperatures T 1 = 343 K and T 2 = 357 K undergo two superionic phase transitions, accompanied by the anomalies of σ ac and ε′. At room temperature and electric field frequency v = 10 3 Hz, σ ac = 5 · 10 − 2 S/m and its activation energy ΔE 1 = 0.47 eV; at temperature T ≥ 357, K σ ac( T) changes with activation energy ΔE 2 = 0.34 eV. In the temperature range 343 ≤ T ≤ 357 K, σ ac( T) dependence does not obey Arrhenius law. In this frequency region two relaxation dispersions of σ ac and ε′ attributed to the ion transport in the grain and grain boundaries of our polycrystals have been found.