Chemical Methodologies for Preparation of Micron and Nanometer Scale Ferrites - A Mini Review of Patents

Ferrites, with wide range of chemical compositions, have been studied extensively over the years as they have a plethora of applications such as magnetic read/write heads, transformer cores, antennas, microwave absorbers, deflecting yoke, high frequency transformers, catalysis, pigments etc. Particles of submicron size have attracted the attention of scientists and technologists in different fields because they exhibit many unique physical properties as compared to those of bulk materials and are in great demand. Traditional high temperature solid-state method for preparation of ferrites is associated with several limitations. The quest for synthesis of ultrafine ferrite materials has led to the development of various preparative methods. Several patents disclose different wet chemical techniques namely sol-gel, coprecipitation, hydrothermal, combustion, spray pyrolysis etc for preparation of variety of ferrites for wide range of applications. In this mini-review, several patented chemical methods have been discussed critically with specific examples along with the effect of synthetic routes on particle size formation. Applications of ferrite powders with different compositions prepared by the above mentioned patented methods have also been discussed in this review.