화학공학소재연구정보센터
Solid State Ionics, Vol.294, 82-89, 2016
Nanolayered solid electrolyte (GeSe2)(30)(Sb2Se3)(30)(AgI)(40)/AgI: A new hypothesis for the conductivity mechanism in layered AgI
Using the laser ablation method, films comprised of alternating layers of AgI and (GeSe2)(30)(Sb2Se3)(30)(AgI)(40)glass were obtained. Individual layer thickness amounts to 10 divided by 15 nm, and the total number of layers is about 100. X-ray diffraction (XRD) and film conductivity measurements were carried out during several cycles of heating up to 200 degrees C and cooling to room temperature. It was established that after three cycles of thermal processing specific lateral conductivity of the film is equal to 0.3 S cm(-1) and conductivity activation energy is equal to 0.07 eV at room temperature. Attempts to explain such a high conductivity value based on XRD results did not yield satisfactory results. However, our first-principle calculations within the density functional theory (DFF) showed that in the free layer composed of four AgI planes a rearrangement occurs, resulting in formation of the stable structure of two silver planes on the inside and two iodine planes on the outside (I-Ag-Ag-I). Rearrangement of similar stack of eight or twelve atomic planes results in formation of two or three I-Ag-Ag-I layers loosely bound to each other, accordingly. This suggests that increase in specific conductivity growth of multilayer film as a consequence of cyclic heating and cooling may be connected with AgI stratification on its boundary with chalcogenide glass and following stabilization of layered phases mentioned above. The existence of an empty space between the layers that is constrained by iodine ion planes should facilitate silver ion diffusion along the layers. (C) 2016 Elsevier B.V. All rights reserved.