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AgGd(MoO₄)₂:Ho³⁺/Yb³⁺ double molybdates with five concentrations of Ho³⁺ and Yb³⁺ were synthesized by the microwave employed sol–gel based process (MES), and the crystal structure variation, concentration effects, and spectroscopic characteristics were investigated. The crystal structures of AgGd_1−x−yHo_xYb_y(MoO₄)₂ (x = 0, 0.05; y = 0, 0.35, 0.4, 0.45, 0.5)at room temperature were determined in space group <i>I</i>4₁/<i>a</i> by Rietveld analysis. Pure AgGd(MoO₄)₂ has a scheelite-type structure with mixed occupations of (Ag,Gd) sites and cell parameters <i>a</i> = 5.24782 (11) and <i>c</i> = 11.5107 (3) Å, <i>V</i> = 317.002 (17) ų, <i>Z</i> = 4. In doped samples, the sites are occupied by a mixture of (Ag,Gd,Ho,Yb) ions, which provides a linear cell volume decrease with the doping level increase. Under the excitation at 980 nm, AGM:0.05Ho,yYb phosphors exhibited a yellowish green emission composed of red and green emission bands according to the strong transitions ⁵F₅ → ⁵I₈ and ⁵S₂/⁵F₄ → ⁵I₈ of Ho³⁺ ions. The evaluated photoluminescence and Raman spectroscopic results were discussed in detail. The upconversion intensity behavior dependent on the Yb/Ho ratio is explained in terms of the optimal number of Yb³⁺ ions at the characteristic energy transfer distance around the Ho³⁺ ion.