Huang, Yu‐ChiehYu‐ChiehHuangChen, Shin‐EnShin‐EnChenTsao, Chuan‐FangChuan‐FangTsaoLin, Yen‐HueiYen‐HueiLinKamiński, MikołajMikołajKamińskiMajewska, NataliaNataliaMajewskaLeniec, GrzegorzGrzegorzLeniecMijowska, EwaEwaMijowskaWang, Han‐ChingHan‐ChingWangCherng, Ding‐HwaDing‐HwaCherngYeh, Ting‐WeiTing‐WeiYehMahlik, SebastianSebastianMahlikLiu, Ru‐ShiRu‐ShiLiu2026-03-022026-03-022026-01-30https://scholars.lib.ntu.edu.tw/handle/123456789/736051Engineering the local crystal field through cation substitution is a widely adopted strategy to modulate the emission wavelength of transition-metal-doped inorganic phosphors in the near-infrared (NIR) region. While redshifting emission is desirable for extending applications into long NIR wavelengths, excessive shifts often lead to increased nonradiative losses due to large Stokes shifts, posing a trade-off between spectral tunability and luminescence efficiency. Herein, we present two series of In3+-substituted phosphors, MgGa1.94−xInxO4:0.06Cr3+ and Mg0.98Ga1.94−xInxO4:0.06Cr3+,0.02Ni2+, with 0.1 ≤ x ≤ 0.9. The incorporation of large In3+ results in lattice expansion and enhanced local disorder, considerably affecting the crystal field environment of Cr3+ and Ni2+. In the first part of the study, the effect of cation substitution on the complex luminescence behavior of Cr3+ in these partially inverse spinel phosphors is systematically investigated. Subsequently, the role of In3+ in tuning the Cr3+/Ni2+-codoped MgGa2−xInxO4 system, wherein Ni2+ emission is successfully redshifted from 1269 to 1429 nm, is explored. The findings of this work underscore the dual role of In3+ as both a structural modulator and an emission-tuning agent, offering a promising strategy for the rational design of broadband, wavelength-adjustable NIR phosphors.encrystal field modulationIn3+ substitutionNi2+ luminescenceredshift tuningspinel phosphorsjournal article10.1002/adom.202503799