Thermochromism and thermal crystal structure evolution of YIn0.9Mn0.1O3

YIn1-x Mn x O3 is a newly discovered inorganic blue pigment whose vivid blue color results from MnO5 trigonal bipyramidal (TBP) polyhedra. Recently, it has been reported that commercial YIn1-x Mn x O3 powders exhibit a temperature-induced color change, i.e., thermochromism. In this study, we investigate the thermochromism and temperature-induced crystal structure evolution of synthetic YIn0.9Mn0.1O3 powders. We observe that a vivid blue color at room temperature is gradually changed to a dark blue color with increasing temperature. This thermochromism is mainly attributed to a broadening of optical absorption bands in the visible and UV regions, and can also be contributed by an enhancement of the UV absorption. Our crystal structure analysis using powder synchrotron X-ray diffraction data not only confirms the thermal expansion and enhanced thermal vibrations of oxygen, but also reveals a temperature-induced deformation of the TBP polyhedra. Based on these results, we discuss a possible mechanism for the thermochromism of the YIn0.9Mn0.1O3 system.