The PS304 powders were prepared by mechanical alloying(MA)using Ni,Cr,Cr2O3,Ag and BaF2/CaF2 powders.The influence of different milling time on powders characteristics was investigated.The results showed that the grain sizes were reduced during mechanical alloying,and the grain sizes of Cr2O3 and Ag were less than 50 nm after 15 h milling.Furthermore,with increase of milling time,the peaks of BaF2/CaF2 in XRD patterns weakened or disappeared,and no new phase was found.So BaF2/CaF2 maybe used to form supersaturated solid solution.EDX analysis showed that the final powder was composite powders.