Red-emitting holmium(III) doped SrNb2O6 and structural stability under pressure

SrNb 2 O 6 and SrNb 2 O 6 :Ho 3+ red phosphors were successfully synthesized by a novel molten salt method. Compared with the traditional synthesis method, the reaction rate is faster at lower temperature. Scanning Electron Microscopy showed the samples are rod-like crystals with an average size of 5 μm. Upon excitation at 638 nm, the samples exhibited red emission peaks in the range of 640–680 nm, which are attributed to the Ho 3+ 5 F 5 → 5 I 8 electronic transition. As the concentration of Ho 3+ increases, the luminescence intensity gradually rises, peaking at x  = 0.03. To explore the stability of the crystal structure under pressure, we conduct high-pressure Raman scattering experiments on SrNb 2 O 6 . Significant changes in the Raman spectra indicate a reversible phase transition between 3.1 and 5.4 GPa. Geometric optimization based on density functional theory suggest that the phase transitions originate from increased coordination of Sr atoms.