Large temperature tuning of the emission color of a phosphor by dual use of Raman and photoluminescence signals

Abstract

The ability to tune the emission color of materials by external stimuli like electric field, pressure, temperature, etc., offers avenues to design light-based sensors and devices. We report here a new strategy which enables large temperature tuning of the emission color of a lanthanide phosphor by combining Raman and photoluminescence (PL) signals. The phenomenon and the associated mechanism, demonstrated on Eu, Er doped BaTiO₃, shows the emission color to change from orange to green when cooled down to 10 K. The large color tuning is a consequence of synergy of the two processes: (i) significant enhancement of the Raman signal due to gradual structural ordering in the rhombohedral ferroelectric phase of the host BaTiO₃ and (ii) anomalous low temperature quenching of the PL emission of the doped Eu³⁺ by trap states. We show that this contrasting temperature effect on the PL and the Raman signals can be used as a powerful strategy to design phosphor materials for high performance optical thermometry.