STRUCTURE AND ELECTRICAL PROPERTIES OF La1.9Sr0.1Ni1-yCoyO4+δ (y=0.10.2) LAYERED COMPOUNDS PREPARED BY A POLYAMINOCARBOXYLATE COMPLEX METHOD

摘要

La1.9Sr0.1Ni1-yCoyO4+δ (y=0.1, 0.2) powders were synthesized by a polyaminocarboxylate complex method. Homogeneous and fine powders (100-200 nm) with a pure K2NiF4 phase were produced by calcining at 900 °C for 2 h in air. The structure and electrical conducting properties of the resulting ceramics sintered at 1450 °C were investigated in comparison with La2Ni0.9Co0.1O4+δ specimen. X-ray diffraction Rietveld refinement results indicated that the ceramic specimens have an orthorhombic structure with Fmmm space group. The comparison of refined structure parameters suggested that the substitution of partial La3+ by Sr2+ at the A-site reduced the length of the Ni/Co-O1 bond in the ab plane, while the Co substitution at the B-site led to an inverse effect. Compared with La2Ni0.9Co0.1O4+δ specimen, La1.9Sr0.1Ni0.9Co0.1O4+δ (y=0.1) ceramic specimen exhibited enhanced electrical conducting properties, offering electrical conductivities of 86-91 S·cm-1 at 600-800 °C. Further increasing the Co content to y=0.2 resulted in a degradation of electrical conducting properties. The variation of the electrical conducting properties with the substitutions was tentatively explained in relation to the crystal structure change.