Optical transitions and radiative properties of green emitting Ho 3+ :YVO 4 phosphor.

The Ho ³⁺ -doped YVO ₄ phosphors were successfully prepared via a sol-gel process in which citric acid was used as a chelating agent. X-ray diffraction (XRD) confirmed the effective inclusion of Ho ³⁺ ions into the host matrix with the formation of single phase YVO ₄ . The surface morphology was observed using SEM, the results of which showed a grain growth propensity and the agglomeration of prepared phosphors. The V-O (VO ₄ ^3- ) vibration mode was analyzed through Fourier transform infrared (FTIR) spectra. The spectroscopic properties were reported through UV-vis-NIR diffuse reflectance and photoluminescence (PL) spectra. The Judd-Ofelt (J-O) intensity parameters Ω ₂ = 0.03 × 10 ^-20 cm ² , Ω ₄ = 0.22 × 10 ^-20 cm ² , and Ω ₆ = 0.23 × 10 ^-20 cm ² obtained for the Y _0.97 VO ₄ :0.03Ho ³⁺ phosphors were used to obtain the total transition probabilities ( A _T ), radiative lifetimes ( τ _rad ) and branching ratios ( β ) for the certain transitions of Ho ³⁺ ions. Under 310 nm UV excitation, the visible emission spectra were measured, and an intense emission was observed around 541 nm (green region) for all the samples. The emission cross-section σ _P ( λ ) was 3.22 × 10 ^-21 cm ² and the branching ratio ( β ) was 0.816; these were investigated to capture the optimal concentration of the Y _0.97 VO ₄ :0.03Ho ³⁺ phosphor. The estimated color coordinates were observed in the green region of CIE diagram. Ultimately, the superior properties ( σ _P ( λ ), β , and color purity) of Y _0.97 VO ₄ :0.03Ho ³⁺ phosphor may make it suitable for green emitting devices.
Competing Interests: There are no conflicts to declare.
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