Revisiting the Spectrum–Crystal Field Relationship of 3d 3 Ion (Mn 4+ /Cr 3+ )‐Activated Phosphors via a Recalibrated Database

ABSTRACT With tunable red‐to‐near‐infrared (NIR) emissions, Mn 4+ ‐ and Cr 3+ ‐activated phosphors have been extensively investigated in recent years and are emerging as alternatives to commercial rare‐earth‐ion‐activated phosphors in various applications. However, the rational design of these phosphors remains a great challenge due to the long‐standing inaccuracy and inconsistency in the spectrum–crystal field relationship. This work aims to revisit and clarify this relationship by constructing a uniformly recalibrated database. We correct empirical formulas and systematically recalculate spectral levels, Racah parameters, and crystal field parameters from reported data. The database integrates these newly derived parameters from diverse host structures, together with standardized configurational‐coordinate models for Mn 4+ /Cr 3+ ions in octahedral sites. By providing an open platform to access accurate information, this reliable database paves the way toward data‐driven design of 3d 3 ion‐activated phosphors with tailored properties.