Strong f–f excitation in hafnium germanate: Near‐UV LED and cathode beam–pumped red phosphor with thermal robustness

Abstract Developing narrowband red phosphors has always been a frontier topic in the phosphor community. In this study, a novel hafnium germanate red phosphor, BaHfGe ₃ O ₉ :Eu ³⁺ , was successfully synthesized by solid‐state reaction method. The phase and crystal structure of BaHfGe ₃ O ₉ were investigated by the Rietveld refinement of powder X‐ray powder diffraction. The band structure was analyzed by density functional theory calculations. Most importantly, the luminescence behavior of phosphors under near‐ultraviolet (n‐UV) light and cathode rays sources was studied in detail to explore the possibility of their applications in white light‐emitting diodes and field emission display. The BaHfGe ₃ O ₉ :Eu ³⁺ phosphor exhibits strong f–f excitation and excellent thermal robustness due to Eu ³⁺ localization in the rigid lattice and asymmetric Ba ²⁺ sites. Under cathode rays and n‐UV light excitation, BaHfGe ₃ O ₉ :Eu ³⁺ exhibits narrowband red light emission peaked at 610 nm. Moreover, BaHfGe ₃ O ₉ :Eu ³⁺ shows excellent saturation resistance and aging resistance. The performance of the LED lamp encapsulated by the BaHfGe ₃ O ₉ :Eu ³⁺ phosphor was studied. The results show that BaHfGe ₃ O ₉ :Eu ³⁺ is a potential red phosphor for multifunctional applications.