The Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ polycrystalline sample was synthesized by the sol-gel process and a subsequent annealing at 1523 K in 1 atm of flowing argon. X-ray diffraction (XRD) analysis and electrical transport properties have been investigated as well. The oxygen non-stoichiometry was determined by iodometric titration. The sample shows adoption of the K 2 NiF 4 -type structure based on a tolerance factor calculation. Rietveld refinement of the crystal structure from X-ray powder diffraction data confirmed that Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ adopts the tetragonal structure (space group I4/mmm, Z = 2). The room temperature unit-cell parameters are determined to be a = 3.82515(2) and c = 12.47528(6) Å. The reliability factors are: R B = 0.043, R wp = 0.012 and χ 2 = 3.00. The Nd 1.7 Ba 0.3 Ni 0.9 Cr 0.1 O 4+δ compound exhibits a semi-conductive behaviour. The electrical transport mechanism has been investigated and it agrees with the adiabatic small polaron hopping model in the temperature range 313 K ≤ T ≤ 708 K.
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