Paper MI-WeM12
Effects of Preheat Treat on the Anisotropy and Particle Size of Sr(TiMn)2Fe8O19 Magnetic Powders

Wednesday, October 17, 2007, 11:40 am, Room 619

The excellent properties of Ti-Mn-substituted ferrite are largely dependent on the characters of multidomain ferrite powders except for Ti-Co-substitution rate. Preheat treatment can influences the formation process of Ba(TiMn)2Fe8O19 powders and further influences the anisotropy of the powders. However this effect has not be reported previously. Ultrafine substituted M-type Sr(TiMn)2Fe8O19 powders were synthesized successfully by sol-gel method. The hydroxide precursor particles were formed in gel solution containing ethanol and water at a ratio of 1:1 and NaOH as coprecipitation agent. The effects of preheat treatment on particle size and c/a value of Sr(TiMn)2Fe8O19 nano powders were studied using XRD and SEM. XRD analysis indicated single phase substituted M-type Sr-ferrite Sr(TiMn)2Fe8O19 were formed by either preheating precursors at 300oC and 400oC respectively for 1h or non-preheating followed by calcining at 900oC for 2h respectively. The particle sizes of powder were changed from 40.8nm to 39.8nm and 41.1nm when the samples were preheated at 300oC and 400oC respectively. Calculation of c/a value with XRD data indicated that the The c/a ratio changed from 3.9145 to 3.9183 and 3.9153 at the preheating temperatures of 300oC and 400oC respectively. A largest c/a value was achieved at preheating temperature of 300oC. SEM analyses revealed that particles were platelet and the decrease in aspect ratio in morphology was accordant to the increase in the c/a ratio with change from non-preheating to preheating at 400oC and to preheating at 300oC.