Chemical and structural effects on ionic conductivity at columnar grain boundaries in yttria-stabilized zirconia thin films

Abstract

This study elucidated the effects of coherence and chemical composition on ionic conductivity at columnar grain boundaries of 6 mol % Y 2 O 3 doped ZrO 2 (YSZ) thin films. The YSZ thin films were deposited with several orientation textures on MgO (100), Al 2 O 3 (102), and SiO 2 -glass substrates using metalorganic chemical vapor deposition (MOCVD). Impedance measurements revealed the total ionic conductivity of the thin films. The activation energy of the ionic conduction of YSZ thin films on MgO or Al 2 O 3 substrates was 90120 kJ/mol. These films showed similar dependence that simply increased along with decreasing coherency at the columnar grain boundaries. However, that of YSZ thin films on SiO 2 glass substrate showed dependence of the coherency at the columnar grain boundaries, but the value is higher than those of the films on MgO or Al 2 O 3 substrates by more than 20 kJ/mol. Structural and compositional analyses clarified that the second phase of SiO 2 is segregated at mid-gaps between columnar grain boundaries in YSZ thin films on a SiO 2 glass substrate. Results show that two factors affect ionic conductivity at the columnar grain boundaries in YSZ thin films: structural coherency and the second phase of ionic insulator.

Investigation of Morphology of Aluminum Co-Doped Scandium Stabilized Zirconia (ScAlSZ) Thin Films

“…Data from several studies [12,13] suggest that columnar grain boundaries act as barriers for oxygen diffusion, and columnar grain boundaries act as rapid diffusion paths. Contrary to the previously published studies, T. Kiguchi et al demonstrated that total ionic conductivity was restricted by the columnar growth, and columnar structure with high coherence was preferred [14,15].…”

“…The influence of deposition rate and substrate temperature on the phase structure of the Cu-Mo films was examined using the approaches based on the phase-field models by Derby et al [35] and Ankit et al [36]. By using the kinetic Monte Carlo approaches, the effects of substrate tilt angle [37], substrate temperature [38], deposition rate [13,14], and composition [39] on the phase structure of nanocomposites have been recently investigated. Bouaouina et al in [37] discovered that the surface roughness and the phase structure of TiN thin films are influenced by the change of substrate tilt angle: an increase in the substrate tilt angle caused an increase in the tilt angle of TiN columns and the surface roughness as well.…”