Abstract:

An in-situ Raman spectra test and study on the hemimorphite were carried out by high temperature Raman spectra technique. The test results show that the characteristic Raman peak of  3,470 cm^-1  representing O-H stretching vibration in the molecular H₂O is disappeared as the hemimorphite being heated  800 K, but the characteristic peak 926 cm^-1 marked Q1 of the main framework [Si₂O₇] is been retained, which means the structure of the hemimorphite is not changed as the H₂O lost. The characteristic peak of 3,580 cm-1 related to stretching vibration of the O-H in the structure water (OH) is disappeared as the sample being heated 1,050 K.The relative intensity of the characteristic peak 926 cm^-1 related to symmetric stretching vibration of nonbridging oxygen of structure unit Q1 gradually decreases, comparing with the growing Raman band of Q0 characteristic peak at 852.4 cm^-1,which indicates the phase transformation of the hemimorphite is started out at 1,050 K. The structure water (OH) is dehydrated completely as the temperature is over 1,100 K, the characteristic peak (3,580 cm^-1) of the structure water (OH) disappears completely, the characteristic peak related to Si-Onb stretching vibration becomes 855 cm^-1, which shows that primary Q1 of the hemimorphite is returned to Q0 (i.e  [SiO₄] ), and which means that the hemimorphite is completely transformed to willemite.

Key words: hemimorphite, in-situ Raman spectra, test, phase transformation, high tempreture