High-temperature behavior of Sr-doped layered cobaltites Y (Ba1 − x Srx )Co2O5.5: phase stability and structural properties

AURELIO, G.; SÁNCHEZ, R. D.; CURIALE, J.; CUELLO, G. J.

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 2010 vol. 22 p. 486001 - 486010

0953-8984

In this paper we present a neutron diffraction in situ study of the thermal evolution and high-temperature structure of layered cobaltites Y(Ba, Sr)Co2 O5+δ . Neutron thermodiffractograms and magnetic susceptibility measurements are reported in the temperature range 20 K T 570 K, as well as high-resolution neutron diffraction experiments at selected temperatures. Starting from the as-synthesized samples with δ ≈ 0.5, we show that the room temperature phases remain stable up to 550 K, where they start losing oxygen and transform to a vacancy-disordered structure with tetragonal symmetry. Our results also show how the so-called ‘122’ structure can be stabilized at high temperature (around 450 K) in a sample in which the addition of Sr at the Ba site had suppressed its formation. In addition, we present the structural and magnetic properties of the resulting samples with a new oxygen content δ ≈ 0.25 in the temperature range 20 K T 300 K.