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Title: Phase equilibria and crystal chemistry of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system at 885 °C in air

The phase diagram of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system at 885 °C in air has been determined. The system consists of two calcium cobaltate compounds that have promising thermoelectric properties, namely, the 2D thermoelectric oxide solid solution, (Ca{sub 3−x}Nd{sub x})Co{sub 4}O{sub 9−z} (0≤x≤0.5), which has a misfit layered structure, and Ca{sub 3}Co{sub 2}O{sub 6} which consists of 1D chains of alternating CoO{sub 6} trigonal prisms and CoO{sub 6} octahedra. Ca{sub 3}Co{sub 2}O{sub 6} was found to be a point compound without the substitution of Nd on the Ca site. The reported Nd{sub 2}CoO{sub 4} phase was not observed at 885 °C. A ternary (Ca{sub 1−x}Nd{sub 1+x})CoO{sub 4−z} (x=0) phase, or (CaNdCo)O{sub 4−z}, was found to be stable at this temperature. A solid solution region of distorted perovskite (Nd{sub 1−x}Ca{sub x})CoO{sub 3−z} (0≤x≤0.25, space group Pnma) was established. In the peripheral binary systems, while a solid solution region was identified for (Nd{sub 1−x}Ca{sub x}){sub 2}O{sub 3−z} (0≤x≤0.2), Nd was not found to substitute in the Ca site of CaO. Six solid solution tie-line regions and six three-phase regions were determined in the CaO–Nd{sub 2}O{sub 3}–CoO{sub z} system in air. - Graphical abstract: Phase diagram of the 1/2 Nd{sub 2}O{submore » 3}–CaO–CoO{sub x} system at 885 °C, showing the limits of various solid solutions, and the tie-line relationships of various phases. - Highlights: • Phase diagram of the CaO–1/2 Nd{sub 2}O{sub 3}–CoO{sub z} system constructed. • System consists of thermoelectric oxide (Ca{sub 3−x}Nd{sub x})Co{sub 4}O{sub 9−z} (0≤x≤0.5). • Structures of (Nd{sub 1−x}Ca{sub x})CoO{sub 3−z} and (CaNdCo)O{sub 4−z} determined.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ; ;  [1] ;  [4]
  1. Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)
  2. Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States)
  3. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)
  4. Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL 60616 (United States)
Publication Date:
OSTI Identifier:
22334271
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 215; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM; CALCIUM OXIDES; COBALT OXIDES; CRYSTALS; NEODYMIUM OXIDES; ORTHORHOMBIC LATTICES; PEROVSKITE; PHASE DIAGRAMS; SOLID SOLUTIONS; SPACE GROUPS; THERMOELECTRIC PROPERTIES