Structure, crystal chemistry and magnetism of rare earth calcium-doped cobaltates: Ln2−xCaxCoO4+δ (Ln = Pr, Nd, Sm, Eu and Gd)
- Thorogood, Gordon J.
- Orain, Pierre-Yves
- Ouvry, Mickael
- Piriou, Bruno
- Tedesco, Tony
- Wallwork, Kia S.
- Herrmann, Jan
- James, Michael
DOIAbstract
Single-phase samples of Ln2−xCaxCoO4+δ (Ln = Pr3+ − Gd3+) around x∼1 have been prepared. For the first time, the phase field for these compounds has been defined using powder X-ray diffraction and a very narrow solid solution was observed. Under our synthetic conditions, the K2NiF4 structure was not formed for the large La3+ ion, or for compositions containing the smaller rare earths ions (<Gd3+) and Y3+. Thermogravimetric analysis indicates average cobalt oxidation states ranging between ∼3.2+ and ∼3.3+. Rietveld refinement of structures using synchrotron powder X-ray diffraction data indicates that the larger rare earth ions LnCaCoO4+δ (Ln = Pr3+ − Sm3+) form tetragonal (I4/mmm) structures at room temperature, while (Ln = Eu3+, Gd3+) crys...
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