1. Sol–gel synthesis and structural characterisation of the perovskite type pseudo solid solution LaNi0.5Cu0.5O3
- Author
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P. Mouron, Fabien Dubois, P. Odier, J. Choisnet, M. Crespin, and M. Municken
- Subjects
Crystallography ,Nickel ,Electron diffraction ,Chemistry ,Neutron diffraction ,Materials Chemistry ,chemistry.chemical_element ,Orthorhombic crystal system ,General Chemistry ,Crystal structure ,Copper ,Solid solution ,Perovskite (structure) - Abstract
The composition LaNi0.5Cu0.5O3−δ has been prepared by heat treating a polyacrylamide xerogel in flowing O2. A perovskite type structure starts to crystallise at 700 °C and is achieved at 1000 °C. TGA data point to the formation of a rather strongly oxidised compound (δ ≤ 0.09). As the solid state reaction of a mixture of La2O3/NiO/CuO powder oxides never yields a perovskite, the part of the sol–gel route in this synthesis proves to be crucial. On the basis of X-ray and neutron diffraction results, the existence of a cupronickelate having a rhombohedral perovskite type structure is proved. Rather unexpectedly, an electron diffraction study of the as-prepared composition at 1000 °C reveals the presence of two sets of perovskite type cupronickelate microcrystals: a copper rich one with a fixed composition 67% Cu and a nickel rich one with a small range of compositions 59 ≤ Ni% ≤ 67. The latter microcrystals feature the rhombohedral LaNiO3 perovskite whereas the former one, due to the partial presence of Cu(II), frequently shows an orthorhombic [2ap√2 × 2ap√2 × ap] supercell. Thus, the composition LaNi0.5Cu0.5O3−δ. has to be understood in terms of a nanoscale segregated pseudo solid solution formed of two lanthanum cupronickelates, enriched in copper and nickel, respectively.
- Published
- 2002
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