Heat treatment and microstructure characteristics of Foitite tourmaline

Foitite tourmaline was heated at 400-1000 ℃ for 2 h.Effect of heat treatment on tourmaline powder phase structure,surface structure of the foitite tourmaline was studied by means of X-ray diffraction,Fourier transform infrared absorption spectroscopy and laser Raman spectroscopy.The results show that tourmaline cell volume decreases with increasing the heat treatment temperature,and has a minimum value at 700 ℃.The heat treatment temperature has great influence on the surface electrical properties of tourmaline,when the temperature reaches 500 ℃,Zeta potential value is up to-48 mV.After heat treatment,the phase of tourmaline has been changed from Foitite tourmaline into Bouguer tourmaline,when the temperature is higher than 900 ℃,tourmaline decomposes to form Fe2O3 and Al4B2O9.Heat treatment can not only oxide Fe2+ to Fe3+,but also change the site of ions in the structure of tourmaline(Y,Z position).