High deposition rate obtained for spin-sprayed Ni-Zn ferrite films without using ammonia ions

Spin-spray ferrite plating without using corrosive ammonia ions was developed and very high deposition rate of 60 nm/min of Ni-Zn ferrite films was achieved by spraying the reaction solution (FeCl₂+NiCl₂+ZnCl₂) and oxidizing solution (NaNO₂+KOCOCH₃) on the rotating glass substrate at 90°C. The change of pH buffer from (NH₄)OCOCH₃ to KOCOCH₃ increased the pH in oxidizing solution from 6.8 to 7.6 and this higher pH expedited the ferrite film formation. The film surface observed in SEM image was smooth, and a large saturation magnetization M_s of 420 emu/cc and low coercivity H_c below 25 Oe were obtained. This film exhibited a high real permeability μ´_r=45 and a high ferromagnetic resonance frequency f_r=500 MHz. The deposition rate increased to 73 nm/min by increasing pH in oxidizing solution from 7.6 to 12.0. Although the film was porous, very high deposition rate of 230 nm/min was obtained for the film using oxidizing solution with high pH of 12.4. This film exhibited μ_r´=15 and f_r=1 GHz, which were comparable to those of commercialized conducted noise suppressors.