Ratiometric temperature sensing behavior of dual-emitting Ce3+/Tb3+ co-doped Na5Y9F32 single crystal with high relative sensitivity

The Na5Y9F32 single crystals doped with fixed 0.5 mol% Ce3+ and various concentrations of Tb3+ (0, 0.4, 0.6 and 0.8 mol%) were grown by Bridgeman method. The luminescent properties, energy transfer (ET) and the ratiometric temperature sensing behavior were studied thoroughly. Under 315 nm excitation, the Ce3+/Tb3+ co-doped Na5Y9F32 single crystal mainly presented two emissions at blue 385 nm (Ce3+:5d -> 4f) and green 545 nm (Tb3+:D-5(4)-> F-7(5)). The color area can undergo from the purple-blue region (0.1643, 0.0768) to the green region (0.2585, 0.3604) by altering the content of Tb3+ ion from 0 to 0.8 mol%. The energy transfer between the Ce3+ and Tb3+ ions was confirmed by decay curves with emission spectra, and the maximum energy transfer efficiency (ETE) were estimated to be 45.1%. The mechanism of dipole-dipole interaction (d-d) for energy transfer from Ce3+ to Tb3+ can be explained by the formula of Dexter's energy transfer. The fluorescence intensity ratio (FIR) of blue and green emission showed a linear relationship with temperature varying from 298 K to 473 K in the 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal. Meanwhile, the 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal possessed higher absolute sensitivity (S-a) of 0.0157 K-1, relative sensitivity (S-r) of 1.18% K-1 and temperature resolution (delta T) of 0.086 K. By using the integrating spheres, the quantum yield (QY) of 0.5 mol% Ce3+/0.8 mol% Tb3+ co-doped Na5Y9F32 single crystal was measured as similar to 16.88%. These excellent optical properties suggest that the Ce3+/Tb3+ co doped Na5Y9F32 single crystal with stable physical-chemical properties could have a far-reaching application prospect for the ratiometric optical thermometry. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the luminescent properties, energy transfer, and ratiometric temperature sensing behavior of Na5Y9F32 single crystals doped with fixed 0.5 mol% Ce3+ and various concentrations of Tb3+. The co-doped single crystal exhibited excellent optical properties and could have a significant application potential.