The Expansion and Shrinkage Characteristics of Ferrites in Firing Process

The expansion and shrinkage behaviors of ferrites in the temperature ranging from room temperature to 1400°C were observed. The curves given by the dilatometer under conditions of increasing temperature are shown in Fig. 5 through Fig. 14. It is evident upon examination of the figures that (1) a sudden expansion occurs at a temperature of about 900°C during firing of Zn-ferrite and Cd-ferrite having the normal spinel structure in the resulting specimen, and above this temperature the shrinkage of specimens is found up to 1400°C, (2) the change in the expansion behavior don't occur for samples of Ni-ferrite and Cu-ferrite having inverse spinal structure and also during reheating of the samples Zn-ferrite and Cd-ferrite cooled after firing, (3) the expansion of the mixture of NiO, ZnO and Fe2O3 during heating tends to increase with increasing ZnO content.