The particle growth at this stage is caused by Ostwald ripening, and the growth rate is determined by the solubility and diffusion coefficient of the product oxide (Rahaman, 2003). Therefore, the heating temperature is a decisive factor in determining the particle size. For example, Bi4Ti3O12 particles in KCl are platelike with the diameter of the plate faces of about 5 μm after heating at 950ºC for 1 h and about 25 μm after 1 h at 1130ºC, and the size can be controlled by selecting the heating temperature and its duration (Kimura & Yamaguchi, 1983). The exceptions are observed in highly faceted particles. The highly faceted surfaces have a high degree of smoothness at the atomic scale and high step energy, and their growth is sluggish (Kang et al., 2009). For example, platelike BaBi4Ti4O15 particles in KCl hardly grow in the particle-growth stage ( Kimura & Yoshida, 2006 ). The top and side faces of the BaBi4Ti4O15 particles are highly faceted; whereas the side faces of Bi4Ti3O12 particles are atomically rough. The growth rate of the BaBi4Ti4O15 particles is substantially zero. Therefore, the control of the particle size by selecting the heating conditions is difficult. Large BaBi4Ti4O15 particles can be obtained from Bi4Ti3O12 using the topochemical micro-crystalline conversion (see 3.4.1) ( Kimura & Yoshida, 2006 ).