The samples subjected to CS at 180 °C/3 h resulted in high densification (94.4%).However, BaTiO3 samples produced by CS had cubic crystal structure and/or amorphous grain boundaries, making the piezoelectric properties inadequate. Accordingly, an additional annealing process(T = 900℃/3 h) to transform the crystal structure into the tetragonal one was conducted and the piezoelectric properties were improved, as shown in Fig. 9(a and b) [203,208].