Hafnium oxide coatings were prepared at various O2/Ar flow ratios by RF(radio frequency) magnetron sputtering on low activation Martensitic steel.The effects of O2/Ar flow ratio on the deposition rate and the properties of HfO2 are studied.The results show that the deposition rate decreases with increasing the O2/Ar flow ratio.Moreover

the coatings prepared at various O2/Ar flow ratios are compact and the main phase of the coatings is monoclinic.Additionally the coatings prepared at the O2/Ar ratios 0.7 and 1.2 were broken down under 1 MV/cm and show poor electrical insulation properties

while the coatings prepared at smaller O2/Ar flow ratios show better electrical insulation properties.