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

TL;DR

This study investigates the high-temperature structural stability and phase transformations of Sr-doped layered cobaltites Y(Ba, Sr)Co2O5+δ using neutron diffraction and magnetic measurements, revealing temperature-induced oxygen loss and structural changes.

Contribution

It provides detailed insights into how Sr doping influences phase stability and structural evolution of layered cobaltites at high temperatures.

Findings

Room temperature phases stable up to 550 K

Oxygen loss leads to vacancy-disordered '112' structure

Sr doping stabilizes the '122' structure at high temperature

Abstract

In this article we present a neutron diffraction in-situ study of the thermal evolution and high-temperature structure of layered cobaltites Y(Ba, Sr)Co2 O5+{\delta}. 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 {\delta} ~ 0.5, we show that the room temperature phases remain stable up to 550 K, where they start loosing oxygen and transform to a vacancy-disordered "112" 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 {\delta} ~ 0.25 in the temperature range 20 K <= T <= 300 K.