Stress- and Temperature-Dependent Wideband Fluorescence of a Phosphor Composite for Sensing Applications

Abstract

As both stress and temperature can alter the lattice of a solid phosphor in a similar way, the dopant rare-earth ion may be used as a probe for either parameter using the same sensing mechanism. Here, a wideband phosphor, YAG:Ce is used as a micro stress sensor at very low magnitudes of compressive stress. The sensing resolution can be smaller than 0.06 N/mm 2 in the range of 0~1.2 N/mm 2 with a sensitivity of 11 cm −1 /MPa. The sensitivity is about a hundred times larger than the coefficient reported under hydrostatic pressure. The barycenter energy of the emission band of a phosphor can be used to indicate stress and/or temperature change, producing a precision beyond the spectroscopic resolution limit. The sensing functions obtained from the barycenter shift are superior to those from peak shifts. The stress/temperature dependent barycenter shift of the observed fluorescence bands of YAG:Ce were similar in magnitude. Mechanisms involving the nephelauxetic effect, crystal field effect and site symmetry of dopant ions are explored as explanations of the experimental phenomena.

Methods for Broadband Spectral Analysis: Intrinsic Fluorescence Temperature Sensing as an Example

“…In this work, all temperature-sensing functions were successfully exploited using the temperature-dependent emission spectra. Similar analysis has also been successfully performed on YAG:Ce broadband emission for stress sensing 25 and rhodamine B fluorescence for pH sensing. Other phosphors with broadband fluorescence can be expected to provide high sensitivity and fine precision with great suitability for particular applications.…”

“…Even though a band barycenter is different from the average energy of excited energy levels, they are still relevant, 23,24 and technically the explanation of such a physical meaning is not essential in the sensing applications. 25 The emission band barycenter was defined as the wavelength, which splits the band, the integral intensity from the wavelength to the band edge is exactly a half of the total emission band area. 25 A particular case is when a band is symmetric in the spectrum, the band barycenter is located at the peak wavelength.…”

“…25 The emission band barycenter was defined as the wavelength, which splits the band, the integral intensity from the wavelength to the band edge is exactly a half of the total emission band area. 25 A particular case is when a band is symmetric in the spectrum, the band barycenter is located at the peak wavelength. As has been shown and proven, the barycenter factor of a fluorescence spectrum band did well when it was applied to characterize the emission band of YAG:Ce.…”

“…As has been shown and proven, the barycenter factor of a fluorescence spectrum band did well when it was applied to characterize the emission band of YAG:Ce. 25 Here, barycenter energies of the emission band of the phosphor sample were retrieved and compared with the peak positions as shown in Figure 4.…”

Physical Manipulation of Lanthanide‐Activated Photoluminescence

“…Creatively, the barycenter energy of emission band was employed as a sensing signal by Zhang et al, [119] which could provide a relatively finer resolution and higher precision in pressure sensing than the classical peak shift method. Using YAG:Ce luminescence, they realized a sensing resolution smaller than 0.06 N mm −2 in the range of 0-1.2 N mm −2 with a sensitivity of 11 cm −1 per MPa.…”