Pressure-triggered polychromatic luminescence in Eu²⁺-activated Ca₈Zn(SiO₄)₄Cl₂ phosphors for high-sensitivity visual optical manometry

To address the inadequate sensitivity of optical manometers, Eu²⁺-activated Ca₈Zn(SiO₄)₄Cl₂ phosphors were designed and synthesized. Under 390 nm excitation, intense green emission from Eu²⁺ was detected in the synthesized phosphors, where the optimal doping content was 2 mol% and the concentration quenching mechanism was contributed by electric dipole-dipole interaction. Moreover, the resulting phosphors exhibited alike high quantum efficiency and good thermal stability. To assess the applicability of these phosphors in optical manometry, pressure-dependent (<i>in situ</i>) X-ray diffraction patterns, Raman and emission spectra were recorded and analyzed. As pressure increases, the studied material undergoes monotonic compression without phase transition, ensuring its operation under high-pressure conditions. Furthermore, the designed phosphors show an obvious spectral redshift at elevated pressure. The emission band centroid shifts from 500.2 to 567.5 nm with the increase in pressure from 0.46 to 20.35 GPa, resulting in polychromatic luminescence and a high sensitivity of d<i>λ</i>/d<i>p</i> = 4.18 nm GPa^-1. Additionally, the full width at half maximum (FWHM) increases with pressure, leading to a sensitivity of dFWHM/d<i>p</i> = 1.33 nm GPa^-1. Further, utilizing the color coordinates as a manometric parameter, the pressure sensing performance of the final products was examined, and the maximum sensitivity was 13.78% GPa^-1. These results indicate that the designed phosphors are promising candidates for broad-range, multi-parameter, and high-sensitivity visual pressure sensors that can be operated in various modes based on emission band centroid, FWHM, and color coordinates.