Electronic properties of La3Ni2O7 and Ln4Ni3O10, Ln=La, Pr and Nd

Single-phase samples of La3Ni2O7-δ with δ=0, 0.08, 0.16 and 0.65, and Ln4Ni3O10. Ln=La, Pr and Nd were prepared and studied by powder X-ray diffraction, thermogravimetric analysis, electrical resistivity and magnetic susceptibility. The as prepared sample, La3Ni2O6.92 and the fully reduced La3Ni2O6.35 are semiconducting, while the oxygenated La3Ni2O7.0 is metallic For Ln4Ni3O10-δ, when Ln = La, 8 is zero and the material is metallic and Pauli paramagnetic; when Ln = Pr and Nd, δ is ~ 0.15 and an anomaly indicating a metal-to-metal transition is observed at 145 K for Pr4Ni3O10-δ, and 165 K for Nd4Ni3O10-δ. The electrical properties of the homologous series Lan+1NinO3n+1 with n=2,3 are discussed and compared in terms of the dimensionality of the crystal lattice and the electronic band structure calculated by the extended Hückel tight binding method.