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Title: Phase equilibria and crystal chemistry of the CaO–½Sm 2O 3–CoOz system at 885 °C in air

The CaO–½Sm 2O 3–CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca 3$-$xSm x)Co 4O 9$-$z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca 3Co 2O 6 which consists of chains of alternating CoO 6 trigonal prisms and CoO 6 octahedra. Ca 3Co 2O 6 was found to be a point compound without the substitution of Sm on the Ca site. A solid solution region of distorted perovskite, (Sm 1$-$xCa x)CoO 3$-$z (0 ≤ x ≤ 0.22, space group Pnma) was established. The reported Sm 2CoO 4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Sm 1+xCa 1$-$x)CoO 4$-$z (Bmab) where 0 < x ≤ 0.15 was found to be stable at this temperature. In the peripheral binary systems, Sm was not present in the Ca site of CaO, while a small solid solution region was identified for (Sm 1$-$xCa x)O(3 $-$z)/2 (0 ≤ x ≤ 0.075). Lastly, ten solid solution tie-line regions and six three-phase regions were determined in the CaO–½Sm 2O 3–CoO z system in air.
 [1] ;  [2] ;  [3] ;  [4]
  1. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  2. Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  4. Illinois Inst. of Technology, Chicago, IL (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Solid State Sciences
Additional Journal Information:
Journal Volume: 48; Journal Issue: C; Journal ID: ISSN 1293-2558
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Phase diagram of CaO-½Sm2O3-CoOz; structure for (Sm1-xCax)2O3-z, and (Sm1+xCa1-x)CoO4-z; thermoelectric oxide system; tie-line phase relationships
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1251268