The A‐C Conductivity of Polycrystalline LISICON, Li2 + 2x Zn1 − x GeO4, and a Model for Intergranular Constriction Resistances

Abstract

The a‐c conductivity of a polycrystalline, Li+ ion conducting solid electrolyte, LISICON, , has been measured over the frequency range 10−3–107 Hz and attention focused on the methods of data analysis. The data show intragranular (bulk) and grain boundary effects in which, for a given sample, both effects are characterized by a similar activation energy; a constriction resistance model for the latter is proposed based on air gaps existing in polycrystalline sinters of less than theoretical density. The data only crudely fit a Debye‐like equivalent circuit, composed of frequency independent resistors and capacitors, but fit well an equivalent circuit that contains Jonscher elements, i.e., frequency dependent admittances, in addition to normal and elements. Two such Jonscher elements are needed, one for the grain boundary and one for the intragranular contribution. With this circuit, departures from ideality in, e.g., the cpmplex impedance, admittance, and electric modulus planes are accounted for.