Energy transfer from the [WO6]6− group to Er3+ in Lu2WO6 and favorable optical thermometry with strong emission color variability†

Non-contact optical temperature measurement has attracted intense attention in recent years due to its advantages of high speed and high safety. In this work, a Lu₂WO₆:Er³⁺ phosphor was successfully prepared by a solid state reaction. The effective energy transfer from the [WO₆]⁶⁻ group to Er³⁺ was proved using the emission spectra and fluorescence lifetime measurements, with an estimated transfer efficiency of 51%. Benefiting from the self-luminescence of the [WO₆]⁶⁻ group, optical thermometry was established based on the fluorescence intensity ratio of [WO₆]⁶⁻ emission to Er³⁺ emission. Remarkably, strong emission color variability from blue to green was observed under 320 nm UV excitation as the temperature increases from 298 K to 548 K, while an opposite trend from green to cyan is observed under 378 nm UV excitation. The maximum relative sensitivity (S_R Max) is 3.37% K⁻¹ (298 K), which is highly superior to most of the previously reported values.