*3.1. Variation of Solution Temperature in the Vicinity of the Sample with Time during SPT*

Figure 2 shows the variation of the solution temperature with time during SPT measured by a thermocouple placed in the vicinity of the sample. The temperature increased rapidly and exceeded 60 ◦C within 3 min after starting SPT, and then increased slowly and reached an almost constant value of 80 ◦C at 30 min. After 30 min of SPT, crystals were precipitated due to heterogeneous nucleation both on the sample surface and in the solution.
