A novel optical thermometry based on the energy transfer from charge transfer band to Eu-Dy ions.

Optical thermometry based on the up-conversion intensity ratio of thermally coupled levels of rare earth ions has been widely studied to achieve an inaccessible temperature measurement in submicron scale. In this work, a novel optical temperature sensing strategy based on the energy transfer from charge transfer bands of W-O and Eu-O to Eu-Dy ions is proposed. A series of Eu/Dy co-doped SrWO is synthesized by the conventional high-temperature solid-state method. It is found that the emission spectra, emission intensity ratio of Dy (572 nm) and Eu (615 nm), fluorescence color, lifetime decay curves of Dy (572 nm) and Eu (615 nm), and relative and absolute sensitivities of Eu/Dy co-doped SrWO are temperature dependent under the 266 nm excitation in the temperature range from 11 K to 529 K. The emission intensity ratio of Dy (572 nm) and Eu (615 nm) ions exhibits exponentially relation to the temperature due to the different energy transfer from the charge transfer bands of W-O and Eu-O to Dy and Eu ions. In this host, the maximum relative sensitivity S can be reached at 1.71% K, being higher than those previously reported material. It opens a new route to obtain optical thermometry with high sensitivity through using down-conversion fluorescence under ultraviolet excitation.