Synergetic coprecipitation effect and coordination effect in the Co-dump coprecipitation process for synthesizing Co-Ti substituted barium M-type ferrite

The chemical coprecipitation process for synthesizing BaCoTiFe_(10)O_(19) ultrafine powders has been investigated by means of corrosion versus pH plot (E-pH plot) for metal element, thermodynamic calculation and co-dump coprecipitation experimentation. The results show that the theoretical pH values of complete coprecipitation of all Fe~(3+), Ti~(4+), Co~(2+) and Ba~(2+) cations were in 9≤pH≤12.2 obtained by E-pH plot and pH≥7.9 obtained by thermodynamic calculation, respectively. The co-dump coprecipitation experiments indicate that the minimum pH value necessary to the formation of single-phase BaCoTiFe_(10)O_(19) under 900℃ for 2h was pH=8.5. It was suggested that three different results and their dependency originate from both synergetic coprecipitation effect of cations and coordination effect of Cl~- anions.