Electrical Conductivities and Conduction Mechanisms of Perovskite‐type Na1‐xKxMgF3 (x = 0, 0.1, 1) and KZnF3

Abstract Electrical conductivities of NaMgF 3 , Na 0.9 K 0.1 MgF 3 , KMgF 3 , KZnF 3 and an aggregate of NaMgF 3 + 2 mol% NaF were measured as functions of temperature and frequency by the complex impedance method. The conductivities of NaMgF 3 and Na 0.9 K 0.1 MgF 3 as a function of temperature show a little jump at 1040 K and 710 K with the phase transition from orthorhombic to cubic. Conductivities of NaMgF 3 KMgF 3 and KZnF 3 increase at 1100 K, 1120 K and 980 K, respectively. These temperatures correspond to the reaction temperatures such as eutectic reaction caused by a slight compositional deviation to alkaline fluoride component side. The extremely high conductivity and the increment of the activation energy were observed just below the melting points of these compounds. The intrinsic conductivity of 0.1 S/m is estimated at most by extrapolation to the melting temperature. From the results on these fluoride perovskite as analog compounds of constituents of the Earth's lower mantle, it is suggested that intrinsic and extrinsic conduction mechanisms are not sufficient to explain high conductivity of uppermost‐part of lower mantle, estimated to be 1‐10 S/m, and an occurrence of low temperature eutectic reaction is necessary to attain such a high conductivity.