Solid solutions of oxysulfides (RE_0.95Ln_0.05)₂O₂S (RE = La, Y; Ln = Ho, Tm) were obtained by hydrogen reduction of the co-precipitated sulfates followed by sulfidation of the reaction products. The crystal chemical characteristics of the obtained compounds were refined by the Rietveld method. Morphological certification of particles in the dynamics of synthesis was performed. Most of the particles produced by chemical reactions have a cut that indicates the formation of a compound with a hexagonal syngony with angles of 60 and 120°. This indicates that the thermal effect of gaseous reagents H₂, H₂S on sulfates leads to heterogeneous reactions of thermal dissociation and the formation of new phases. Steady state luminescence properties displayed characteristic sharp bands corresponding to 4f-4f transitions. Luminescence decay curves of all studied samples showed monoexponential decay with microsecond and hundreds microsecond lifetimes depending on doping ions. Calculated color coordinates of Ho³⁺ and Tm³⁺-doped powders make them promising candidates to be used as phosphors.