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We aim to conduct a complete study on the unexpected structure evolution behavior in Cr3+-doped phosphors. A series of Ga2–xScxO3:Cr3+ phosphors are successfully synthesized and confirmed through structural studies, while the lattice parameters change unexpectedly. The unique partial substitution (∼87%) of Sc3+ in the octahedral site is demonstrated via Rietveld refinement. Therefore, the bond valence sum calculation explains the reason for this particular Sc3+ concentration. The photoluminescent bandwidth and electron–lattice coupling energy initially increase and then decrease, implying an inhomogeneous broadening effect. Time-resolved spectra and electron paramagnetic resonance are utilized to further examine the subtle change in the microstructures and the second coordination sphere effect of Cr3+. Ga1.594Sc0.4O3:0.006Cr3+ exhibits high internal quantum efficiency (99%) and high phosphor-converted light-emitting diode output power (66.09 mW), demonstrating its capability as an outstanding infrared phosphor. This work will motivate further research on unexpected partial substitution during the solid solution process.
Fang et al. (Wed,) studied this question.