Samples of POCl3-SnCl4-235UO2-Dy3+ solutions have been prepared to investigate conversion of energy of heavy charged particles into optical radiation. Experimental data on radioluminescent characteristics of Dy3+ upon homogenous excitation of solutions by uranium α-radiation have been obtained. The efficiency of conversion of the energy of uranium α-particles into light energy depends on the Dy3+ concentration and the Dy3+ luminescence lifetime τ. At [Dy3+] = 0.2 mol/L and τ = 550 μs, the conversion efficiency is 0.12 ± 0.01% for the luminescent transition 4F 9/2 → 6H 13/2 (λmax = 574 nm) or 0.20 ± 0.01% for the visible and near IR regions of Dy3+ luminescence.