Peculiar properties of crystal-chemical stucture of spinels of the system Mg(FexCr2-x)O4 obtained through the hydroxide coprecipitation method and solid state technology

Abstract

Using the coprecipitation method of metal hydroxides, magnesium ferrite-chromites of the system Mg(FexCr2-x)O4 were synthesized, and a comparative analysis of crystal-chemical parameters of the obtained samples with similar samples, made through the solid state technology was performed. The precipitation method provides high dispersion, lower sintering temperature and more even distribution of components in the sintered ferrite. It was found that in samples, synthesized through the hydroxide coprecipitation method, the value of lattice constant is greater and reversibility degree is lower compared with samples synthesized through the solid state technology. The formation of magnesium ferrite-chromites from coprecipitated hydroxides is completed at temperatures 500-700 ºC lower than with the standard solid state technology using oxides. The dimensions of the crystallites in the samples obtained through the hydroxide coprecipitation method are within 50-130 nm and are smaller than samples, obtained through the solid state technology (200-400 nm). The changes in dispersion and ionicity degree of the chemical bond, depending on the composition and synthesis method were monitored. The obtained results demonstrate the possibility of synthesis through the hydroxide precipitation of ferrites of the system Mg-Fe-Cr and allow to predict their crystal-chemical parameters.