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

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.