Shear stress response and fluorescence piezo-spectroscopic properties of SrSiAlN3:Eu2+/epoxy composite

Phosphor SrSiAlN3:Eu2+ was used for stress sensing for the first time. It was mixed with strain gauge epoxy H610 and cured to form an active composite. Stress-dependent fluorescence of the composite was calibrated on a customized shear test bench. Fluorescence intensity ratio (FIR) played the role of stress sensing signal, and presented a sensing function FIR = 0.9841 + 0.04610 with a linearity of 2.7% and a resolution of 0.002 MPa. Such a resolution could be superior for three to six orders of magnitude to the standard fluorescence piezo-spectroscopy (ruby under stress load). Regarding barycenter wavelength as another stress sensing signal, the fluorescence band of the composite was also observed slightly shifting towards blue under an increasing shear stress. The calibrated sensitivity of the sensing system was 0.713 nm/MPa. A linearity of 3.4% and a resolution of 0.003 MPa were determined accordingly. With respect to the fine resolution(s) of the experimental system, the phosphor composite could provide both sensing functions for piezo-spectroscopic applications.