Ultrastable, Self‐Recoverable and Broadband‐Tunable NIR Mechanoluminescence in Cr 3 + ‐Activated Tantalates

ABSTRACT Near‐infrared mechanoluminescence (NIR ML) materials hold promise for in situ stress visualization and non‐destructive in vivo diagnostics, but most reported systems suffer from pre‐irradiation requirements, narrow emission bandwidth, or poor environmental stability. Herein, we report a family of Cr 3+ ‐activated double perovskite tantalates that overcome these limitations via compositional engineering. Through controlling the local crystal‐field, the NIR ML without pre‐irradiation can be continuously tuned across a broad wavelength range (782–844 nm), reaching a maximum full width at half maximum (FWHM) of 160 nm. Mechanistic studies reveal that the self‐recoverable ML arises from local piezoelectric‐field‐driven carrier transportation, rather than the trap‐controlled process. Remarkably, the broadband NIR ML exhibits exceptional resistance to water and organic solvents without noticeable performance degradation even after over 3000 h of direct immersion, outperforming the state‐of‐the‐art NIR‐ML material (i.e., CaZnOS:Nd 3+ ). Accordingly, the ML composite film enabled real‐time and high‐resolution biomechanical imaging through 5 mm of pork tissue. This work introduces a robust design strategy for high‐performance self‐recoverable NIR ML material systems, establishing a versatile platform for advanced applications such as stress sensing and non‐destructive in vivo diagnostics.