Understanding Intermediate-Range Order in Amorphous Nitridic Ceramics: A ²⁹Si{¹¹B} REDOR/REAPDOR and ¹¹B{²⁹Si} REDOR Study

The structural organization of nitridic ceramics in the system Si/B/N/C on an intermediate length scale is studied using 29 Si{ 11 B} rotational echo adiabatic passage double resonance (REAPDOR) and 11 B{ 29 Si} rotational echo double resonance (REDOR) NMR spectroscopy. The experiments are performed on a 100% 29 Si enriched 29 Si 3 B 3 N 7 ceramic material, obtained by ammonolysis and subsequent pyrolysis of the single-source precursor molecule ((trichlorosilyl)amino)dichloroborane (TADB, Cl 3 29 SiNHBCl 2 ). Simulations of the resulting double resonance curves on the basis of multiple spin interactions are presented. The double resonance data is supported by additional 11 B and 29 Si static dipolar spin−echo experiments. The combined results obtained from the different experimental approaches indicate an unexpected connectivity motif in these ceramics, characterized by regions of mainly Si−N−Si linkages and islands of predominantly B−N−B connectivities.