Lithium-boron-aluminum glasses and glass-ceramics doped with Eu3+: A potential optical thermometer for operation over a wide range of temperatures with uniform sensitivity

Abstract

• Eu-doped Li 2 O - B 2 O 3 −Al 2 O 3 glasses and glass ceramic were synthesized. • The calculated Judd-Ofelt intensity parameters of these media were ~ 10 −20 cm −1 . • The glass ceramic showed greater emission intensity than the precursor glass. • They are efficient probes for optical thermometry using peak-valley ratio method. • Nearly constant relative sensitivity was obtained over a wide temperature range. In this work, lithium-boron-aluminum (LBA) glasses doped with Eu 3+ were produced by the traditional melting method. These precursor glasses (PG) were heat treated at 400 and 450 °C for 6 h to produce glass-ceramics (GC). The X-ray diffraction measurements showed the formation of a crystalline phase. In the LBA GCs, crystal growth is nucleated at the surface and an increase in the emission intensity of the heat-treated glasses compared with the PG was observed. Spectral analysis of the luminescence indicated that Eu 3+ occupies low-symmetry site (asymmetry ratio ≈ 4) and without an inversion center. The emission spectra were analyzed using Judd-Ofelt theory and the intensity parameters Ω 2 , Ω 4 and Ω 6 were calculated. The values of these parameters were not significantly affected by the heat treatment process. The application of these materials as optical temperature sensors using the valley-peak intensity ratio (VPIR) was investigated using the multi-peak spectral profile of the 5 D 0 → 7 F J luminescence bands of Eu 3+ . We estimated the relative sensitivity, the figure-of-merit of the thermometer, to be as high as 0.40 ± 0.02% K −1 . Interestingly, some VPIR that were explored presented a constant value for the relative sensitivity across the temperature interval used in our experiment (between 312 and 393 K), which is advantageous for sensor operation over a broad temperature range.