Understanding intermediate-range order in amorphous nitridic ceramics: A Si-29{B-11} REDOR/REAPDOR and B-11{Si-29} REDOR study

The structural organization of nitridic ceramics in the system Si/B/N/C on an intermediate length scale is studied using Si-29(B-11) rotational echo a diabatic passage double resonance (REAPDOR) and B-11(Si-29) rotational echo double resonance (REDOR) NMR spectroscopy. The experiments are performed o n a 100% Si-29 enriched (Si3B3N7)-Si-29 ceramic material, obtained by ammon olysis and subsequent pyrolysis of the single-source precursor molecule ((t richlorosilyl)amino) dichloroborane (TADB, (Cl3SiNHBCl2)-Si-29). Simulation s of the resulting double resonance curves on the basis of multiple spin in teractions are presented. The double resonance data is supported by additio nal B-11 and Si-29 static dipolar spin-echo experiments. The combined resul ts obtained from the different experimental approaches indicate an unexpect ed connectivity motif in these ceramics, characterized by regions of mainly Si-N-Si linkages and islands of predominantly B-N-B connectivities.