Films of ZnS and MgP2 have been prepared by Ar-ion assisted deposition. The packing density of the MgF2 films has been increased from-0.8 without ion-bombardment to 0.9-0.95 with bombardment as determined by:the wavelength-shift measurement after moisture adsorption of filter. Experiment found thatabsorption and scattering losses increased with the high energy ion (>lkeV) bombardment and the low energy ion(<0.7 keV) bombardment is shown to increase significantly the abrasion resistance and adherence of films without significantly degrading their optical performance. This technique is of important for application in praparing durable coatings on temperature sensitive substrates.