Upconversion Photoluminescence Properties of PbY₂(MoO₄)₄:Er³⁺/Yb³⁺ Phosphors Synthesized by Microwave Sol–Gel Method

Abstract

PbY 2− x (MoO4 )4:Er3+/Yb3+ phosphors with the correct doping concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) were successfully synthesized using the microwave sol–gel method; their upconversion photoluminescence properties were investigated in detail. Well‐crystallized particles, formed after heat‐treatment at 900 °C for 16 h, showed a fine and homogeneous morphology with particle sizes of 2–5 µm. Under excitation at 980 nm, the PbY 1.7(MoO4 )4:Er0.1 Yb 0.2 and PbY 1.5(MoO4 )4:Er0.05 Yb 0.45 particles exhibited a strong 525‐nm emission band, a weak 550‐nm emission band in the green region, and a very weak 655‐nm emission band in the red region. The Raman spectra of the doped particles indicated the presence of strong peaks at higher and lower frequencies induced by disordered structures of PbY 2− x (MoO4 )4 by the incorporation of the Er3+ and Yb3+ ions into the crystal lattice, which resulted in the unit cell shrinkage accompanying the new phase formation of the MoO 4−x group.

Triple molybdate scheelite-type upconversion phosphor NaCaLa(MoO4)3:Er3+/Yb3+: structural and spectroscopic properties

“…The variation of the green-to-red ratio with the ytterbium content increase is rather common and was observed earlier for several hosts. [15][16][17][37][38][39] The Er 3+ ion activator is the luminescence center of these UC particles and the sensitizer Yb 3+ effectively enhances the UC luminescence intensity because of efficient energy transfer from Yb 3+ to Er 3+ . The concentration quenching effect can be explained by the energy transfer between the nearest Er 3+ and Yb 3+ ions.…”

“…Er 3+ and Yb 3+ ion co-doping can remarkably enhance the UC efficiency for the shift from the infrared to visible light due to the efficiency of the energy transfer from Yb 3+ to Er 3+ . [15][16][17] For the preparation of the double molybdate NaLn(MoO 4 ) 2 , several processes have been developed via specific preparation processes, including solid-state reactions, 4,8,[18][19][20][21] the sol-gel method, 22,23 Czochralski growth, [24][25][26][27] the hydrothermal method, [28][29][30][31][32] the microwave assisted hydrothermal method 33 and pulsed laser deposition. 34 Nevertheless, it is necessary to create new triple molybdate compounds for the observation of the UC photoluminescence in the materials and to search for features such as a well-defined morphology and stable UC luminescent properties.…”