Synthesis and properties of Na2Sr1.5Nb3−xRuxO10 (x = 0.5, 1.0, 1.5) series compounds

Na2Sr1.5Nb3−xRuxO10 (x = 0.5, 1.0, 1.5) series compounds with Ruddlesden-Popper (RP) structure were synthesized by solid state reaction. The compounds were characterized by X-ray diffraction, thermal gravimetric analysis and X-ray photoelectron spectroscopy. The RP phase forms at 1050 °C. The compounds decompose when exposed to the ambient air at room temperatures for a long time. The cryogenic electrical behavior of Na2Sr1.5Nb1.5Ru1.5O10 can be described by variable range hopping (VRH) model. The electronic conduction at temperatures below 52 K is via two-dimensional hopping mechanism and three-dimensional hopping above that temperature. The high temperature electrical behavior of all compounds accords well with ρ = ρ0 exp(Ea/kT) relation. Both the resistivity and activation energy decrease with increasing Ru content in the compounds. The Na+ ions in all specimens are immobilized and thus cannot be exchanged with other ions such as Li+, K+.