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

The effects of tensile strain on the electronic properties of Cu- and Ga-doped Pr_1.9NiO₄ (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.