Structural and electrical properties of strontium substituted Y2BaNiO5

• Limit of solid solution of system Y2−xSrxBaNiO5 shown to be at x = 0.2.
• Characterization of the electrical behaviour in the positive temperature range, 100–700 °C.
• Conductivity shown to be independent of pH2O and pO2.
• Low activation energies demonstrated for electrical conduction (0.216–0.240 eV).

The Y2−xSrxBaNiO5 (x = 0, 0.1, 0.2 and 0.3) acceptor substituted system has been synthesized by solid state reaction. Structural and microstructural properties have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Lattice volume is shown to decrease linearly with increasing Sr content until composition x = 0.2, highlighting the limit of the solid solution. The electrical response in the temperature range (700–100 °C) was assessed by A.C. impedance spectroscopy in wet and dry O2 and N2 atmospheres. Conductivity measurements as a function of oxygen partial pressure (pO2) were also performed. The data reveal that the conductivity Y2BaNiO5 can be increased by one and half orders magnitude by Sr-doping and is independent of both water vapour and oxygen partial pressures (pH2O and pO2). The low activation energy for electrical conduction (0.216–0.240 eV) suggests a thermally activated electron hopping mechanism, while the observed pO2 and pH2O independence of conductivity suggests that charge compensation for Sr is predominantly by formation of Ni3+ rather than formation of oxygen vacancies.