Thirty-Fold Increase in Relative Sensitivity of Dy3+ Luminescent Boltzmann Thermometers Using Multiparameter and Multilevel Cascade Temperature Readings

Abstract

The sensitivity of luminescent Boltzmann thermometers is restricted by the energy difference between the thermally coupled excitement levels of trivalent lanthanides, and their values further decrease with increases in temperature, rendering their use at high temperatures difficult. Here, we demonstrate how to overcome this sensitivity limitation by employing multiparameter and multilevel cascade temperature readings. For this purpose, we synthesized Dy3+:Y2SiO5, a phosphor whose emission is known to begin quenching at very high temperatures. Its photoluminescence-emission features, later used for thermometry, consisted of two blue emission bands centered around 486 nm and 458 nm, and two bands centered around 430 nm and 398 nm, which were only visible at elevated temperatures. Next, we performed thermometry using the standard luminescence-intensity ratio (LIR) method, which employs the 4F9/2 and 4I15/2 Dy3+ levels’ emissions and the multilevel cascade method, which additionally uses the 4G11/2 level and overlapping intensities of 4I13/2, 4M21/2, 4K17/2, and 4F7/2 levels to create two LIRs with a larger energy difference than the standard LIR. This approach yielded a sensitivity that was 3.14 times greater than the standard method. Finally, we simultaneously exploited all the LIRs in the multiparameter temperature readings and found a relative sensitivity that was 30 times greater than that of the standard approach.