Alloyed nanocrystalline Ba0.5Sr0.5FCl0.5Br0.5 doped with Sm3+ ions was prepared by a facile ball milling method at room temperature. Spectral hole-burning properties of Sm2+ ions from X-irradiated sample were investigated in the F-7(0)-D-5(0) transition between 2.5 K and room temperature. The alloying allows a "chemical" broadening of the inhomogeneous width of the F-7(0)-D-5(0) f-f transition to 40 cm(-1); spectral holes with a homogeneous width of 5 cm(-1) can be burnt, yielding a figure-of-merit of Gamma(inh)/Gamma(hom) = 8. Mechanochemical preparation methods have a significant potential for the preparation of functional materials for applications in frequency domain optical data storage and as X-ray storage phosphors by allowing the preparation of tailored solid solutions.