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

GABRIELA AURELIO; RODOLFO D. SÁNCHEZ; JAVIER C. CURIALE; GABRIEL CUELLO

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 2010 vol. 22 p. 48600101 - 48600110

0953-8984

In this paper we present a neutron diffraction in situ study of the thermal evolution andhigh-temperature structure of layered cobaltites Y(Ba, Sr)Co2O5+δ. Neutronthermodiffractograms and magnetic susceptibility measurements are reported in the temperaturerange 20 K < T < 570 K, as well as high-resolution neutron diffraction experiments at selectedtemperatures. Starting from the as-synthesized samples with δ ≈ 0.5, we show that the roomtemperature phases remain stable up to 550 K, where they start losing oxygen and transform toa vacancy-disordered structure with tetragonal symmetry. Our results also show how theso-called ?122? structure can be stabilized at high temperature (around 450 K) in a sample inwhich the addition of Sr at the Ba site had suppressed its formation. In addition, we present thestructural and magnetic properties of the resulting samples with a new oxygen content δ ≈ 0.25in the temperature range 20 K < T < 300 K.