“…The stretching vibration of the secondary amine (-NH=) is specifically responsible for the absorption peak at 3360 cm −1 , and the peaks at 2960 cm −1 , 2925 cm −1 , 2854 cm −1 , and 1406 cm −1 correspond to the asymmetric stretching vibration of the methyl groups in the aliphatic hydrocarbon chain, the symmetric stretching vibration of the methylene groups, and the bending vibration of the methylene groups. Peaks at 1164 cm −1 , 1054 cm −1 , 775 cm −1 , and 692 cm −1 in the spectra of quartz are, respectively, typical peaks of Si-O, Si-O-Si, and O-Si-O [28][29][30]. Therefore, the distinctive vibrations of Si-O, Si-O-Al, Si-O-Si, and Al-O-Al are responsible for the peaks in petalite at about 1180 cm −1 , 1066 cm −1 , 1007 cm −1 , and 730 cm −1 , respectively.…”