Effect of A -site cation ordering on the thermoelectric properties of the complex cobalt oxides Gd 1-x Sr x CoO 3-δ ( x  = 0.8 and 0.9)

Abstract

The effect of substitution of Sr 2+ ions for Gd 3+ ions on the phase composition, electrical resistivity, thermoelectricity, and thermal conductivity of rare-earth cobalt oxides Gd 1-x Sr x CoO 3-δ (x = 0.8 and 0.9) has been investigated. It has been determined that at the investigated strontium concentrations, the single-phase disordered nonstoichiometric cubic perovskites and superstructures with ordered Sr 2+ /Gd 3+ ions and anion vacancies can be formed. The influence of ordering/disordering of Gd and Sr cations over crystal-lattice Asites on the thermoelectric figure of merit and sample stability at high temperatures has been studied. The thermoelectric figure of merit of the disordered samples was found to exceed by far the analogous parameter of the ordered samples, which allows us to consider the disordering as a way of improving the thermoelectric parameters. Two contributions to the conductivities are discussed: hightemperature thermoactivation and low-temperatures variable range hopping. The parameters of the Mott electronic structure, including DOS N(ε F), hopping energy ε (the energy of hopping conductivity activation), and hopping length R h , have been estimated

Order–disorder transition in the Dy0.2Sr0.8CoO3-δ rare-earth cobalt oxide solid solutions: Structural and thermoelectric properties

“…Recently, we have found that, upon the transition from a layered tetragonal phase with the ordered distribution of Gd/Sr ions in cobaltite Gd 0.2 Sr 0.8 CoO 3-δ to a cubic phase with the random arrangement of Sr 2+ and Gd 3+ cations in the A sites of the crystal lattice, many physicochemical properties, including the value of oxygen nonstoichiometry and type of the ordering of oxygen vacancies [12,13], change. This affects the mobility of lattice oxygen/oxygen vacancies and, consequently, the oxygen-ion conductivity.…”