Gumann Sina, Nestle Nikolaus, Liebau-Kunzmann Verena, Riedel Ralf
Darmstadt University of Technology, Institute of Condensed Matter Physics, Hochschulstr. 6, D-64289 Darmstadt, Germany.
Solid State Nucl Magn Reson. 2007 Apr;31(2):82-90. doi: 10.1016/j.ssnmr.2007.02.003. Epub 2007 Mar 1.
Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C.
含锂的硅（氧）碳氮化物陶瓷（SiCN(O):Li）通过含锂（聚）硅氮烷的前驱体到陶瓷的转变合成。前驱体通过用正丁基锂对2,4,6-三甲基-2,4,6-三乙烯基环三硅氮烷进行锂化以及通过商业聚（有机硅氮烷）VL20与金属锂反应获得。在氩气中于200至1400摄氏度之间（ΔT = 200摄氏度）进行退火处理，得到含锂的硅（氧）碳氮化物。X射线粉末衍射表明，所得的SiCN(O):Li陶瓷在1000摄氏度以下基本为非晶态，在较高温度下形成LiSi₂N₃、石墨和碳化硅作为晶相。进行了⁷Li MAS NMR光谱分析以研究含锂相的结构并研究金属Li与聚硅氮烷的反应路径。基于NMR光谱，在不同温度下获得的SiCN(O):Li陶瓷的化学位移几乎没有差异。因此，Li主要被认为与作为杂质元素存在的N和O配位。弛豫时间测量表明，最易移动的Li⁺物种似乎存在于在600至1000摄氏度的热解温度范围内获得的产物中。
