Effects of Three-Dimensional Strain on Electric Conductivity in Au-Dispersed Pr_1.90Ni_0.71Cu_0.24Ga_0.05O_4+δ

Abstract

The effects of tensile strain on the electronic properties of Cu- and Ga-doped Pr1.9NiO4 (PNCG) were investigated. The difference in the thermal expansion coefficient between PNCG (α = 13.5–13.9 × 10–6 K–1) and Au (α = 14.2 × 10–6 K–1) can induce tensile strain in PNCG, resulting in changes in electrical conductivity. Hall-effect measurements indicated that the tensile strain stabilized the oxidized state of PNCG, and the electrical conductivity increased because of the increased hole concentration. This suggests that the tensile strain affected the valence numbers of cations in PNCG, increasing the hole concentration and raising the conductivity. Furthermore, the BO6 octahedral distance in the K2NiF4 structure was increased by the induced strain, decreasing the hole mobility.

Strain Effects on Oxygen Reduction Activity of Pr2NiO4 Caused by Gold Bulk Dispersion for Low Temperature Solid Oxide Fuel Cells

“…529 eV), which could be assigned to oxygen at interstitial sites. , A comparison of the XPS results for 0 and 1 mol % Au revealed the peak areas show that the reduced state (ca. 529 eV) of oxygen was increased by the addition of 1 mol % Au, which was correlated with an increase in interstitial oxygen (δ) of the PNCG . As shown in Figure , the peak area at ca.…”

“…In the K 2 NiF 4 structure, interstitial positions in a rock salt block are considered to be fast oxide ion mobile routes because of a large free volume . In our previous work, we reported the oxygen permeation properties of PNCG with a dispersion of Au and suggested that the oxide ion conductivity increased . On the other hand, an increase in bulk oxygen dissociation and electronic density is also related with increased surface ORR because the charge transfer step is reported as the rate-determining step for oxygen dissociation on the cathode oxide .…”

“…However, the peak position returned to high angle at 7 mol % Au. Therefore, tensile strain was successfully introduced and is attributed to the difference in the TECs of Au and PNCG. , However, with an excess amount of Au, phase separation and/or large diameter Au particles were annealed and the tensile strain formed. From this result, 5 mol % Au was the upper limit to generate tensile strain while maintaining the tetragonal structure of PNCG.…”

“…Some strategies have been suggested for strain inducement, such as TEC mismatch between a metal and metal oxide or lattice mismatch between a substrate and epitaxial oxide film. − For example, a metal oxide was sintered at high temperature after metal particles were dispersed in the oxide, and large strain was introduced at the interface between the metal particles and the metal oxide during cooling due to differences in their TECs. We have previously reported on strain induced by TEC mismatch between Au (as a metal) and PNCG (as metal oxide), so-called three-dimensional (3D) tensile strain. , Although tensile strain in PNCG was successfully induced by a dispersion of Au particles and the fundamental electrical properties were investigated, the performance of such a material as a cathode for SOFCs has not been reported until now. The effects of strain on surface activity to oxygen dissociation have been reported recently and have attracted much interest. − However, these studies were mainly performed using thin films and far from the structure of a realistic electrode.…”

“…We have previously reported on strain induced by TEC mismatch between Au (as a metal) and PNCG (as metal oxide), so-called three-dimensional (3D) tensile strain. 25,26 Although tensile strain in PNCG was successfully induced by a dispersion of Au particles and the fundamental electrical properties were investigated, the performance of such a material as a cathode for SOFCs has not been reported until now. The effects of strain on surface activity to oxygen dissociation have been reported recently and have attracted much interest.…”