Figure 2(a) shows X-ray diffraction

Figure 2(a) shows X-ray diffraction of the initial powder (BT-powder) and sintered specimens, respectively. It appears all the specimens possess a perovskite phase as a major phase. The small amount of the impurity phase (BaCO3) is only seen in the initial powder and disappeared after CSP. The molten hydroxide may have provided the thermodynamically stable conditions that preferred the perovskite formation over the BaCO3, as already observed under hydrothermal conditions. No obvious peaks from hydroxide phases are found in X-ray diffraction pattern, probably due to their small proportion and/or their low crystallinity. Figure 2(a-2) shows a peak from 200 reflection. The single peak of 200 reflection indicates that all the specimens are the pseudo-cubic structure. The peak shape is nearly same in the form of the ceramic pellet and grindederamic (Figure S5).