Effect of green density on the templated-grain growth in CuO-doped (K,Na)NbO3 ceramics

Templated-grain growth (TGG) behavior was investigated in 1 mol% CuO-doped (K0.5Na0.5)NbO3 (KNN) ceramics. Textured green sheets were prepared by a tape casting process using a slurry containing NaNbO3 template crystals and fine KNN matrix powders. Laminated ceramic green sheets with different green densities were annealed at temperature ranging from 1,100 to 1,160 °C. Highly textured ceramics were obtained from both low green density (LGD) and high green density (HGD) samples. The TGG and the densification proceeded non-uniformly in the LGD sample. The LGD sample showed high porosity after annealing while the HGD sample displayed high density. Both the HGD and LGD samples displayed similar texture development with increasing sintering time and temperature despite a large difference in the sintered density. These results demonstrate that the pore drag force is not the critical factor for the TGG in CuO-doped KNN textured ceramics, which is contrary to previous reports.