Synthesis and characterization of luminescent properties of ceramics derived from polysilylcarbodiimides

Abstract

The luminescence properties related to the thermal polymer/ceramic conversion behavior of silicon dicarbodiimide {SDC, [Si(N=C=N) 2 ] n } have been investigated. SDC was synthesized by the non-oxidic solgel condensation reaction of silicon tetrachloride with bis(trimethylsilyl)carbodiimide. As-synthesized SDC showed no luminescence under UV light, while heat-treated SDC showed an appreciable photoluminescence (PL) and the maximum visible PL emission intensity was achieved by heat treatment at 400°C. Even after the heat treatment up to 970°C, the SDC preserved most of the N=C=N groups to keep whitish gray color without distinct free carbon formation, and emitted visible blue luminescence. The 400°C-heat treated SDC exhibited the intense luminescence excited at 281 and 379 nm wavelengths, while there was no PL emission excited by the N=C=N groupderived host absorption at 214 nm. The PL properties of the heat-treated SDCs could be correlated with their preservation of the local structure including N=C=N groups and defects formation during the heat treatment. Moreover, Eu 3+ -modified SDC was prepared by the same solgel method using Eu(III) chloride as the Eu 3+ -source. The results of Si NMR spectroscopic analyses revealed a complex formation between the Eu(III) chloride and bis(trimethylsilyl)carbodiimide. As a result, the Eu 3+ -modified SDC exhibited a characteristic PL red emission at around 600 nm attributed to the f-f-transition of Eu .

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…There has been little work to utilise this carbodiimide-based sol-gel chemistry to process silicon carbonitrides. However the luminescence properties of materials based on [Si(NCN)2]n polymers have been examined -blue emission was observed in amorphous ceramics fired at low temperature such that they still contained NCN groups, and addition of EuCl3 to the monomer solution before gelation allowed the incorporation of Eu 3+ ions with characteristic red emission [240].…”