“…In the HCL, Hf and HNO 3 leached sample, the peaks were broader and had lower intensity, indicating the presence of a signi cant amount of amorphous silica(Kim et al, 2017). The diffraction angles showed a further shift to lower values, with the (100) peak at 19.6° and the (110) peak at 23.8°, suggesting a further reduction in the size of the silica crystals and a change in the Miller index(Wu et al, 2018).According to X-ray diffraction analysis, the quartz (SiO 2 ) phase exhibited peaks at 2θ values of 26.4°, 32.4°, 46.4°, and 56.8°, corresponding to the (100), (110), (101), and (211) planes, respectively. These peaks were also observed at 2θ values of 26.1°, 32.2°, 46.2°, and 56.5° in the sample leached with HCL and Hf, and in the sample leached with HCL, Hf, and HNO 3 .…”