The stretching mode [TeO4] trigonal pyramidal with bridging oxygen are located at
660 cm1 and the band at 740 cm1 is related to the presence of non bridging oxygens (NBO) associated to structural units different than [TeO4]:[TeO3+1] polyhedrons and [TeO3] trigonal pyramids [15–17]. The band centered at around 446 cm1 is related to the symmetric stretching vibrations of Te–O–Te