“…As shown in Fig. 2, the main absorption bands in the range of 400-1000 cm À 1 are attributed to the responses of Bi-O, W-O and W-O-W stretching modes in Bi 2 WO 6 crystal [24,25]. The band at 1100 cm À 1 is assigned to the Si-O vibration in silicates [26], further confirming the existence of Bi 12 SiO 20 .…”