resumo
The Y-2 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 degrees C) was assessed by A.C. impedance spectroscopy in wet and dry O-2 and N-2 atmospheres. Conductivity measurements as a function of oxygen partial pressure (pO(2)) 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 (pH(2)O and pO(2)). The low activation energy for electrical conduction (0.216-0.240 eV) suggests a thermally activated electron hopping mechanism, while the observed pO(2) and pH(2)O independence of conductivity suggests that charge compensation for Sr is predominantly by formation of Ni3+ rather than formation of oxygen vacancies. (C) 2014 Elsevier B.V. All rights reserved.
palavras-chave
MAGNETIC-PROPERTIES; HALDANE-GAP; R2BANIO5 R; DIFFRACTION; OXIDES; POLYMORPHISM; HOLE; YB
categoria
Chemistry; Materials Science; Metallurgy & Metallurgical Engineering
autores
Nasani, N; Ramasamy, D; Antunes, I; Singh, B; Fagg, DP
nossos autores
Isabel Alexandra Gonçalves Antunes
Investigador Júnioragradecimentos
The authors acknowledge kind support from the FCT, FEDER and COMPETE, PTDC/CTM/100412/2008, PTDC/CTM/105424/2008, and Narendar Nasani is grateful to FCT for doctoral research Grant SFRH/BD/80949/2011. Isabel Antunes is thankful to the FCT for doctoral research grant SFRH/BD/76738/2011.