Electrical properties of layered perovskite-type palladium oxides

Electron-doping into Nd₂PdO₄ and Ba₂PdO₂F₂ with the same structure as in the electron-doped high-T_c superconductor T′-Nd_2-xCe_xCuO₄ has been tried by introducing oxygen vacancies or intercalating Li⁺ ions in order to bring about superconductivity. Polycrystalline samples of T′-Nd₂PdO₄ were synthesized by the solid-state reaction method using a NaCl-flux technique. In order to introduce oxygen vacancies, the samples were annealed at 600-700 °C in flowing gas of argon or in vacuum. It has been found that the value of the electrical resistivity of T′-Nd₂PdO_4-δ decreases down to ∼10 Ω cm through the annealing in vacuum, however, but it still remains semiconductive. Polycrystalline samples of T′-Ba₂PdO₂F₂ were prepared by the low-temperature fluorination of Ba₂PdO₃ using ZnF₂ as a fluorinating agent. The intercalation of Li into T′-Ba₂PdO₂F₂ was tried using an electrochemical technique. However, it has been found from the ICP-AES analysis that Li⁺ ions are not intercalated into T′-Ba₂PdO₂F₂.