Eu²⁺-Activated KGa₅S₈: A New Super-Sensitive Green Emitting Phosphor for Pressure Sensing

Optical pressure sensing plays a crucial role in high-pressure research and materials science, yet luminescent manometers that combine high sensitivity with a visually detectable color change remain rare. In this work, a novel Eu²⁺-activated KGa₅S₈ green-emitting phosphor has been successfully synthesized, demonstrating remarkable piezochromic properties. When the applied pressure is varied from 1 atm (∼0.1 GPa) to 10.44 GPa, a significant spectral redshift is observed in the sample. This results in a visually striking color transition, shifting from a green emission peaking at 541 nm to a red emission peaking at 697 nm. This transition yields an exceptionally high-pressure linear sensitivity of dλ/dP = 14.49 nm/GPa, marking it as the highest value reported to date among pressure-sensing materials with emission in the visible range. The multicolor emission variation is attributed to pressure-induced electronic structure modulation, enabling sensitive pressure detection. This study provides a new piezochromic phosphor with record sensitivity and an obvious visual color change, offering a promising candidate for high-pressure sensing applications.