Modeling grain growth experimentally is illustrated in Figure 24.22. Such studies are an extension of the measurement of GB migration. In Ostwald ripening the driving force is the reduction of total energy. The mechanism may require diffusion of one component through the other, as shown in Figure 24.23, which thus imposes an activation barrier An application in which secondary recrystallization has been useful is in the development of textured ceramics in which the preferred orientation is produced by seeding. (More about this is given later.) The magnetically hard ferrite, BaFel20,9, may thus be produced with large grain sizes. For this ferrimagnet it is desirable to obtain a high density as well as a high degree of preferred or in the sintered product. Particles of the powdered material can be oriented to a considerable extent by subjecting them to a high magnetic field while forming. On sintering there was a 57% alignment after heating to 1250°C On further heating at 1340°C the preferred orientation