Up-conversion luminescence and highly sensing characteristics of Er3+/Yb3+ co-doped borophosphate glass-ceramics

Er3+/Yb3+ co-doped phosphate glass ceramics (GC) with a cubic KAlSi2O6 type structure were successfully fabricated by traditional melt-quenching technique and subsequent heat treatment. Structural characterization of the GC was achieved by X-ray powder diffractometer (XRD) combined with transmission electron microscope (TEM). The up-conversion (UC) optical properties were systemically investigated through absorption spectra, photoluminescence spectra, pump power dependent UC emission spectra, and UC decay curves. The possible energy transfer process and the transition channels were analyzed by using energy level diagram. Results show that the UC luminescence performance of the GC was enhanced compared to precursor glass (PG). Moreover, the temperature dependent UC emission spectra of the GC were measured in the temperature range of 298-798K under 980 nm laser excitation. Combined with the fluorescence intensity ratio (FIR) technique, the UC emissions of Er3+/Yb3+ co-doped GC with two thermally coupled energy levels (TCELs) of 525 nm (Er3+: H-2(11/2) -> I-4(15/2) ) and 549 nm (Er3+: S-4(3/2) -> I-4(15/2)) were studied as a function of temperature in the range of 298-798K. For optimized Er3+/Yb3+ co-doped GC, the theoretical maximum value of relative sensitivity Sr-max is 1.67 % K-1 at 298 K, and absolute sensitivity Sa-max is 4.59 x10(-3) K-1 at 570 K, which indicates that the Er3+/Yb3+ co-doped phosphate GC is a very promising candidate for optical temperature sensors with higher sensitivity.