Synthesis of Zn-doped talc in hydrothermal atmosphere.

Zn-doped talc were synthesized under hydrothermal conditions at constant reaction time and pressure of 160 hours and 2 kbar respectively, at three different temperatures (300, 500 and 650 degrees C) with pH-values of 5 and 7. The starting materials and run products were characterized by X-ray powder diffraction (XRPD), scanning electron microscopy with annexed energy-dispersive spectrometry (SEM-EDS), differential scanning calorimetry thermogravimetric analysis (DSC-TG) and Fourier transform infrared (FT-IR). The results showed that the temperature, pH-value of the reaction mixture and amount of zinc in the starting mixture affected the growth of the Zn-doped talc. When synthesized at low temperature talc presents low crystallinity, flawed morphology but higher content in zinc in its lattice. A thermal treatment at, or above 500 degrees C allowed a significant flaw reduction in talc morphology, a higher crystallinity and a lower content in dopant. When large amounts of Zn were present in the starting mixtures, Zn-doped talc grew small in size and poorly shaped. The effect of Zn doping on some chemical/physical characteristics of the synthesized talc was also discussed.