Non-hydrolytic sol–gel synthesis of tantalum sulfides

Non-hydrolytic sol–gel synthesis provides a low temperature solution based approach to solid-state materials. In this work, reactions of TaX5 (X = F, Cl, Br, I) with the thio-ethers di-tert-butylsulfide and hexamethyldisilathiane were carried out in chloroform or acetonitrile. The influence of synthetic parameters such as temperature, reaction time, starting sulfur to tantalum ratio, and solvent volume were explored, and optimized conditions for the preparation of phase pure crystalline TaS2 were established. Amorphous powders were recovered for most of the samples, but crystalline 1T- and 3R-TaS2 modifications could be selectively prepared by heat treatments of the as-recovered precursors at 700 and 800 °C, respectively. The crystallite sizes could be adjusted by tuning the starting sulfur to tantalum ratios, and by choice of solvent. For specific conditions, nanocrystalline 1T-TaS2 was directly recovered from solution. To our knowledge, this is the first time that crystalline TaS2 was directly obtained from low temperature solution based routes.