## 3 Results and Discussion
### Characterization and Optical Properties of S-Phosphor
After 1 h of solvent heat treatment, the surface of the blocks started to become uneven, and cracks started to appear at the edges (Figure 4b). At 4 h of reaction, the cracks in the blocks became more pronounced (Figure 4c). When the reaction was carried out for 8 h, cracks appeared in most of the phosphor powder and even in most of the small particles of phosphor, and the number of cracks increased dramatically (Figure 4d). At 12 h (Figure 4e), the phosphor surface was covered by a large number of small irregular particles of phosphor, the powder was eroded significantly, the cracks turned into grooves, and the \"tearing\" phenomenon began to appear. At 24 h of reaction (Figure 4f), the number of cracks in the powder was significantly reduced and was  
Figure 3: (**a**) Excitation spectra, (**b**) emission spectra, and (**c**) afterglow decay curves of original phosphors and S-phosphor. Figure 2: Size distribution of: (**a**) Original phosphor and (**b**) S-phosphor. not obvious; the powder became uneven, and rough \"pits\" appeared. Scanning electron microscopy (SEM) analysis of the \"cracked\" parts of the powder (Figure 4g,h) revealed that the fracture was uneven, the surface was rough, and irregular grooves appeared, similar to the phenomenon of wall cracked. In addition, a large number of submicron-sized phosphors were agglomerated at the cracked area (Figure 4i). Therefore, this work proposes a mechanism for the fragmentation of phosphor powder (Figure 5); with the beginning of the solvothermal reaction, part of the large-size phosphor powder was gradually eroded and peeled off from the smooth surface of the powder by the influence of high-temperature and high-pressure conditions and stirring in the reaction kettle, and the corners of the powder diamonds also gradually became smooth. As the reaction proceeded, the surface of the powder became rougher and rougher, and cracks began to appear, gradually cracking. At the same time, some of the stripped small-sized phosphor was attached to the surface of the block. As the reaction continued, the large-sized powder was \"torn\" into small-sized particles, which ultimately led to a reduction in the overall particle size of the phosphor. In order to explore the applicability of this solvent heating method to the same phosphor with different particle sizes, SAOED with 6.32 \(\upmu\)m, 24.6 \(\upmu\)m, and 61.2 \(\upmu\)m particle sizes were also subjected to cyclohexane solvent heating in this work. The emission spectra  
Figure 4: Scanning electron microscopy (SEM) images of cracks appearing during the reaction process. (**a**) Untreated commercial phosphor; (**b**) 1 h; (**c**) 4 h; (**d**) 8 h; (**e**) 12 h; (**f**) 24 h; (**g**-i**) block tearing surface. Figure 5: Crushing mechanism of block phosphor. (Figure 6a) show that the optical properties of SAOED with different particle sizes were weakened to a certain extent after solvent heat treatment, which corresponds to the reduction of the overall particle size from 6.32 \(\upmu\)m to 4.86 \(\upmu\)m (Figure 6b), 24.6 \(\upmu\)m to 12.6 \(\upmu\)m (Figure 6c), and 61.2 \(\upmu\)m to 45.8 \(\upmu\)m (Figure 6d). The commercial Sr4 Al14O25 phosphor with 20 \(\upmu\)m particle size and the commercial Sr2 MgSi2O7 phosphor with 20 \(\upmu\)m particle size were also taken to explore the universality of this solvent-heating method for different phosphors with the same particle size. It can be found that, after solvent-heating treatment, the optical properties of the two were weakened compared with those of the commercial phosphors before the treatment (Figure 6e,f), and the changes in the particle size were consistent with the results of the previous experiments. The changes in particle size were also consistent with the previous experimental results, and the overall average particle size after the solvent thermal reaction was reduced compared with that of the untreated commercial phosphor. Moreover, the volume percentage of submicron size increased compared with that before the reaction (Figure 6g,h).