LAUSR

Abstract An experiment was performed to investigate whether CaCO 3 and SiO 2 addition enhances the magnetic properties of cobalt-free M-type Sr ferrites, in which experimental parameters such as additive composition and the CaCO 3 /SiO 2 ratio were changed. The specimens were prepared using conventional ceramic techniques. CaCO 3 addition promoted densification and uniform grain growth, resulting in high remanence; however, with the simultaneous addition of CaCO 3 and SiO 2 , coercivity decreased to 3046 Oe in Sr ferrite hard magnets without Co 3 O 4 . SiO 2 addition suppressed grain growth. The addition of appropriate concentrations of CaCO 3 and SiO 2 as additives after calcination was shown to be very beneficial for tailoring a dense microstructure with relatively small grains. A CaCO 3 /SiO 2 ratio of approximately 1.8 was found to be optimum, and the magnetic properties of B r  = 4.3 kG, i H c  = 3.7 kOe, and ( BH ) max  = 4.5 MGOe were obtained for Sr ferrite hard magnets without Co 3 O 4 , which are acceptable for motor applications under output power