Preparation of SrGd2(MoO4)4:Er3+/Yb3+Phosphors by the Microwave-Modified Sol-Gel Method and Their Upconversion Photoluminescence Properties

Abstract

SrGd 2-x (MoO₄)₄:Er 3+ /Yb³ phosphors with doping concentrations of Er 3+ and Yb 3+ (x = Er 3+ + Yb 3+ , Er 3+ = 0.05, 0.1, 0.2, and Yb 3+ = 0.2, 0.45) were successfully synthesized by the cyclic microwave-modified sol-gel method, and their upconversion mechanism and spectroscopic properties have been investigated in detail. Well-crystallized particles showed a fine and homogeneous morphology with grain sizes of 2-5 μm. Under excitation at 980 nm, SrGd 1.7 (MoO₄)₄:Er 0.1 Yb 0.2 and SrGd 1.5 (MoO₄)₄:Er 0.05 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 domination of strong peaks at higher frequencies of 1023, 1092, and 1325 cm -1 and at lower frequencies of 223, 2932, 365, 428, 538, and 594 cm -1 induced by the incorporation of the Er 3+ and Yb 3+ elements into the Gd 3+ site in the crystal lattice, which resulted in the unit cell shrinkage accompanying a new phase formation of the [MoO₄] 2- groups.