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. 2011. Structure, crystal chemistry and magnetism of rare earth calcium-doped cobaltates: Ln2−xCaxCoO4+δ (Ln = Pr, Nd, Sm, Eu and Gd). Solid State Sciences, 13 (12) : 2113-2123.

Quartile : Q2, Sujet : PHYSICS, CONDENSED MATTER / Quartile : Q3, Sujet : CHEMISTRY, INORGANIC & NUCLEAR / Quartile : Q3, Sujet : CHEMISTRY, PHYSICAL

Résumé : 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+) crystallised with orthorhombic (Bmab) structures. The evolution of structure between the low temperature orthorhombic form and the high temperature tetragonal form was investigated between 80 K and 575 K using high-resolution synchrotron X-ray powder diffraction. Orthorhombic to tetragonal transitions were observed for SmCaCoO4.17 (T∼230 K), EuCaCoO4.13 (T∼320 K) and GdCaCoO4.11 (T∼465 K). Magnetic measurements for LnCaCoO4+δ (Ln = Pr3+ − Gd3+) indicate paramagnetic behaviour along with weak antiferromagnetic interactions and Co3+ in a 6t2g low-spin state. PrCaCoO4.17 was found to order antiferromagnetically below 15 K.

Classification Agris : 000 - Autres thèmes

Champ stratégique Cirad : Hors axes (2005-2013)

Auteurs et affiliations

• Thorogood Gordon J., Australian Nuclear Science and Technology Organisation (AUS)
• Orain Pierre-Yves, Université Paul Cézanne (FRA)
• Ouvry Mickael, Australian Nuclear Science and Technology Organisation (AUS)
• Piriou Bruno, CIRAD-PERSYST-UPR Biomasse-énergie (FRA) ORCID: 0000-0001-5780-3216
• Tedesco Tony, Australian Nuclear Science and Technology Organisation (AUS)
• Wallwork Kia S., Australian Synchrotron (AUS)
• Herrmann Jan, National Measurement Institute (AUS)
• James Michael, Australian Nuclear Science and Technology Organisation (AUS)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/577909/)

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