Electrical properties of layered perovskite-type palladium oxides

Electron-doping into Nd2PdO4 and Ba2PdO2F2 with the same structure as in the electron-doped high-Tc superconductor T′-Nd2−xCexCuO4 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′-Nd2PdO4−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.