【Member Papers】Structural evolution and photoluminescence modulation by Gd³⁺ in Tb³⁺-doped Ga₂O₃

      Researchers from the Guilin University of Electronic Technology, The 34th Research Institute of China Electronics Technology Group Corporation and Ningbo University have published a dissertation titled "Structural evolution and photoluminescence modulation by Gd³⁺ in Tb³⁺-doped Ga₂O₃" in Materialia.

Project Support

      This research was funded by Guangxi Science and Technology Plan Project (AD24010060, AD25069103), National Natural Science Foundation of China (NO.52262022, 62205080, 62174041, 62361022), Guangxi Key Laboratory of Precision Navigation and Application (NO.DH202202), Project of Guangxi Graduate Education (NO.YCBZ2025153), Innovation Project of GUET Graduate Education(NO.2025YCXS037).

Background

      Semiconductor-based phosphor materials have garnered growing interest in recent years owing to their wide-ranging applications in fluorescent anti-counterfeiting, ultraviolet photodetectors, semiconductor lasers, and biomedical imaging technologies Among numerous semiconductor materials, gallium oxide (Ga₂O₃) stands out due to its ultrawide bandgap (∼4.9 eV), high thermal stability, and suitability as a host lattice for rare-earth (RE) activators such as Ce³⁺, Dy³⁺, and Eu³⁺. These characteristics have expanded the application of Ga₂O₃ in power electronics, electroluminescent devices, and bio-imaging platforms.

      RE ions are known for their sharp 4f–4f transitions, high color purity, long lifetimes, and exceptional chemical stability, making them highly suitable dopants for luminescent applications such as solid-state lasers, optical storage, and full-color displays. When trivalent RE ions are introduced into oxide matrices, their partially filled 4f orbitals interact with the matrix's d- or p-orbitals, enabling efficient f–f transitions and thereby enhancing the host's optical performance. The incorporation of RE ions endows the Ga₂O₃ host with efficient 4f–4f transitions originating from the dopants, thereby significantly enhancing the luminescence efficiency of the material. 

Abstract

      A series of (Gd_xGa_1-x)₂O₃: Tb³⁺phosphors (x = 0, 0.1, 0.3, 0.5, 0.7) were synthesized via a co-precipitation method to explore the dual role of Gd³⁺ ions in modulating the crystal phase, band structure, and luminescent performance. The results reveal that Gd³⁺ ions significantly enhances the green emission intensity of Tb³⁺, and this enhancement effect exhibits a clear dependence on the concentration of Gd³⁺ ions. As the Gd³⁺ content increases, the dominant phase transitions from α-Ga₂O₃ to Gd₃Ga₅O₁₂ and Gd₃GaO₆, reflecting effective regulation of crystal structure. Photoluminescence and energy transfer analyses suggest that Gd³⁺ acts not only as an efficient sensitizer to facilitate energy transfer to Tb³⁺, but also as a structural modulator that widens the bandgap and suppresses non-radiative losses. These results demonstrate the dual function of Gd³⁺ as both an optical sensitizer and a structural stabilizer, offering a viable strategy for optimizing the design and performance of rare-earth-doped oxide phosphors.

Conclusion

      This study systematically investigated the effect of Gd³⁺ concentration on the structural evolution and photoluminescent properties of (Gd_xGa_1-x)₂O₃: Tb³⁺ phosphors. With increasing Gd³⁺ content, the host lattice underwent a distinct phase transition from α-Ga₂O₃ to cubic Gd₃Ga₅O₁₂ and then to orthorhombic Gd₃Ga₁O₆. Among these, the garnet-type Gd₃Ga₅O₁₂ phase obtained at x = 0.3 provided the most favorable host environment for Tb³⁺ activation, yielding the strongest green luminescence.

      Gd³⁺ plays a dual role: as a structural stabilizer, it improves crystallinity and phase uniformity; as an optical sensitizer, it enables efficient Gd³⁺→Tb³⁺ energy transfer while suppressing non-radiative recombination. This dual-function mechanism provides an effective strategy for tuning the optical properties of rare-earth-doped oxide phosphors. Compared with previously reported Ga₂O₃:Tb³⁺ systems, the optimized (Gd_0.3Ga_0.7)₂O₃: Tb³⁺ composition significantly outperforms them in luminescence efficiency and color tunability. These findings deepen the understanding of Gd³⁺-mediated luminescence enhancement and establish principles for designing high-performance green phosphors.

      Looking forward, further optimization through co-doping strategies, defect engineering, and thermal treatment control could broaden the application of such materials in solid-state lighting, display technologies, and advanced optoelectronic devices.