Crystal Structure and Coordination of B-Cations in the Ruddlesden-Popper Phases Sr3-xPrx(Fe1.25Ni0.75)O7- (0 x 0.4)

• Compounds Sr3-xPrxFe1.25Ni0.75O7- with 0 x 0.4 and Ruddlesden-Popper n = 2 type structures were synthesized and investigated by X-ray and neutron powder diffraction, thermogravimetry, and Mossbauer spectroscopy. Both samples, prepared at 1300 degrees C under N-2(g) flow and samples subsequently air-annealed at 900 degrees C, were studied. The structures contained oxygen vacancies in the perovskite layers, and the Fe/Ni cations had an average coordination number less than six. The oxygen content was considerably higher for air-annealed samples than for samples prepared under N-2, 7 - = similar to 6.6 and similar to 5.6 per formula unit, respectively. Mossbauer data collected at 7 K, below magnetic ordering temperatures, were consistent with X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) results. The electrical conductivity was considerably higher for the air-annealed samples and was for x = 0.1 similar to 30 Scm(-1) at 500 degrees C. The thermal expansion coefficients were measured in air between room temperature and 900 degrees C and was found to be 20-24 ppmK(-1) overall.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Ruddlesden-Popper structure

oxygen non-stoichiometry

crystal structure

Mossbauer spectroscopy

electrical conductivity

thermal expansion

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