LAUSR

Abstract Hydrothermal process was employed to synthesize the Yb3+/Tm3+, Yb3+/Ho3+ and Yb3+/Tm3+/Ho3+ doped BaMoO4 octahedron microcrystals (0.50–5.0 µm). The synthesized phosphors have scheelite tetragonal structure. The elemental mapping suggests the uniform distribution of elements in the samples. The oxidation state of samples were investigated by X-ray photoelectron spectroscopy (XPS) which indicates the existence of Ba2+, Mo6+, O, Yb3+, Tm3+ and Ho3+ in samples. The presence of rare earth ions was also verified by observation of specific absorption peaks in diffuse reflectance spectra (DRS). The tunable multicolor upconversion (UC) emissions were successfully obtained under 980 nm NIR excitation by precisely adjusting the concentration of rare earth ions. The as prepared sample exhibits blue, green and red emission as a result of energy transfer from the Yb3+ to Tm3+ and Ho3+ ions. The power dependent UC emission spectra show the two photonic processes. The energy transfer mechanism from Yb3+ to Tm3+ and Ho3+ was explained via an energy level analysis.