Thermochromism in (Ba,Sr)-Mn oxides

Manganese based ceramic samples with composition given by the formula MeMnO₃ (Me=Ba, Sr) were prepared by solid state reaction. The preparation conditions were varied over a wide range of temperatures and the optimum sintering temperature was obtained. These materials present a change of color at low temperature (at approximately 140 K). To find the probable reason for the change of color, the materials have been characterized by various advanced techniques like X-ray diffraction (XRD), photoluminiscence, scanning and transmission electron microscopy (SEM and TEM). Studies were made at room and at low temperature. These thermochromic materials have hexagonal perovskite-like structure.